Understanding industrial action
What is industrial action?
Industrial action refers to concerted activities by employees intended to put pressure on an employer during a dispute, typically over terms and conditions of employment. It is not defined in statute but generally includes strikes, action short of a strike (such as overtime bans or work-to-rule), picketing, and other collective acts designed to disrupt normal working arrangements. Industrial action may be official (authorised by a trade union) or unofficial (not authorised), and its lawfulness depends on strict compliance with statutory balloting and notification procedures. Most industrial action involves a breach of contract, but legal protections may apply if statutory requirements are met, including immunity for unions and protection from dismissal for employees during protected periods.
What is a strike?
A strike is a form of industrial action where employees collectively refuse to work as a means of exerting pressure on their employer in relation to a trade dispute. Participation in a strike usually constitutes a breach of the employment contract, and employers are entitled to withhold pay for the period of non-attendance. For a strike to be lawful and protected, it must be called following a properly conducted ballot and appropriate notice to the employer. Employees dismissed for taking part in a protected strike within the first 12 weeks are generally entitled to claim unfair dismissal, provided the action meets statutory requirements.
Action short of strike action
Action short of a strike encompasses collective measures where employees continue to work but deliberately withdraw some element of their labour. Examples include working to rule (performing duties strictly according to contract), go-slows (deliberately reducing work rate), overtime bans, or refusing to cover for absent colleagues. While some forms of action short of a strike may not always breach the contract, others can, depending on the terms of employment. Employers may respond by withholding pay proportionate to the work not performed or refusing to accept partial performance, provided this is communicated clearly to staff. Legal protections for employees and unions depend on whether the action is official and properly balloted.
What is picketing?
Picketing involves employees and union representatives standing outside a workplace to explain the reasons for industrial action and to peacefully persuade others to join or not cross the picket line. Lawful picketing must take place at or near the picketer’s place of work, be peaceful, and not involve obstruction, intimidation, or criminal behaviour. The Code of Practice recommends no more than six pickets per entrance, and a picket supervisor must be appointed by the union. Unlawful picketing, such as blocking access or using threatening behaviour, may result in criminal or civil liability for individuals or the union.
What is unofficial strike action and secondary action?
Unofficial strike action occurs when industrial action is not authorised or endorsed by a recognised trade union, or where the union has repudiated the action. Employees participating in unofficial action have no statutory protection from dismissal, and employers may dismiss selectively without risk of unfair dismissal claims, except in limited protected circumstances. Secondary action, also known as sympathy action, is when workers take industrial action in support of employees of a different employer involved in a separate dispute. Secondary action is unlawful in the UK, and participants are not protected from dismissal or detriment. Both unofficial and secondary actions carry significant legal risks for employees and unions.
Legal framework and requirements
Legal requirements for lawful industrial action
Industrial action is only lawful if it is in contemplation or furtherance of a trade dispute, and both the union and employees comply with a complex statutory regime. This includes authorisation by the union, a properly conducted ballot, and strict adherence to notification and balloting requirements. If these steps are not followed, the union and employees risk liability for breach of contract, injunctions, and loss of statutory protections such as immunity from tort claims and unfair dismissal protection for employees. Secondary action (sympathy strikes) and action supporting closed shop practices are unlawful regardless of procedure, and criminal liability may arise from unlawful conduct during action, such as trespass or harassment.
Trade union balloting requirements for official action
A union must conduct a secret postal ballot of all members it reasonably believes will be induced to take action, excluding those who cannot be induced (e.g., leavers). The ballot must be supervised by an independent scrutineer if over 50 members are balloted. The union must give the employer at least seven days’ notice of the ballot, provide a sample voting paper three days before the ballot, and announce the result to both members and the employer as soon as practicable. For important public services, at least 50% turnout is required, and at least 40% of all eligible members must vote in favour. The ballot mandate lasts six months (or four weeks to commence action), after which a fresh ballot is needed.
Legitimate action after a strike ballot
If the ballot is successful and all statutory requirements are met, the union can call for industrial action within six months of the ballot. Action must be limited to those balloted and must be in line with the type of action voted for (strike or action short of strike). The union must serve at least 14 days’ notice of intended action to the employer (seven days by agreement). Only those employees included in the ballot may be induced to participate. Any deviation—such as calling unballoted members—risks the action being unlawful and losing legal protections.
Guidance on notice to strike
Unions must give employers a minimum of 14 days’ written notice before industrial action begins, unless the employer agrees to a shorter period of seven days. The notice must specify the categories and number of employees affected, their workplaces, and how these figures were determined. Failure to provide correct notice invalidates the action’s legal protections, exposing the union to injunctions and damages. The employer can use this period for contingency planning or to challenge the legality of the action if procedural defects are identified.
Informing employees and employers of strike action
After a successful ballot, the union must inform all members entitled to vote of the ballot result and notify the employer as soon as possible. When calling action, the union must communicate to members when and how action will be taken, and by whom. Employers may ask employees if they intend to strike, but employees are not legally required to respond in advance. The union’s communications must be clear and only directed to those who were balloted, to avoid unlawful inducement.
Minimum service levels (MSLs) and when they apply
MSLs are statutory requirements introduced by the Strikes (Minimum Service Levels) Act 2023, allowing the government to set minimum service levels in sectors such as health, fire and rescue, education, transport, border security, and nuclear decommissioning. Where MSL regulations are in force, employers may issue a “work notice” to the union specifying which employees must work during a strike to maintain the minimum service. The union must take reasonable steps to ensure compliance; failure to do so removes statutory immunity and unfair dismissal protection for both the union and affected employees. As of July 2025, MSLs are in force for passenger rail, ambulance, and border security services, with further sectors pending. Employers must consult unions before issuing work notices, and notices must not name more workers than reasonably necessary. The statutory Code of Practice details the reasonable steps unions must take, and failure to comply may be considered in legal proceedings.
Participation in industrial action
Participation of non-union members in strikes and industrial action
Non-union employees who fall within the same bargaining unit covered by a lawful industrial action ballot may lawfully participate in the strike or other action, provided it is official and all statutory procedures have been followed. These employees are entitled to the same protections from dismissal as union members during the protected period (typically the first 12 weeks of lawful action). Union membership is not required to participate, and employers may not compel or prevent lawful participation on that basis. Recognition of the trade union is not a legal prerequisite for the action to be protected, so long as the union has properly conducted the ballot and complied with legal notice requirements.
Who can join a picket line
Employees participating in official industrial action—whether union members or not—are legally permitted to join a peaceful picket at or near their normal place of work. The picket must comply with the Code of Practice on Picketing, including:
Being peaceful and non-obstructive;
Not involving intimidation or harassment;
Limiting numbers (recommended maximum of six pickets per entrance);
Having a designated picket supervisor, if organised by a trade union.
Picketing is limited to those directly involved in the dispute; individuals from other employers or unrelated sites (so-called flying pickets) are not permitted under UK law. Union representatives and officials may join picket lines to support their members, but the action must remain peaceful and within legal limits.
Crossing a picket line
Anyone has the legal right to cross a picket line, including:
Employees who choose not to strike;
Visitors, contractors, or suppliers;
Other workers not part of the dispute.
Pickets must not prevent or physically obstruct anyone from entering the workplace. Peaceful persuasion is lawful, but aggressive or coercive behaviour may result in civil or criminal liability. Employees refusing to cross a picket line where they are not part of the lawful action may be viewed as engaging in unlawful secondary action, which is not protected and may expose them to disciplinary measures.
Rights and protections
Dismissal for participating in lawful industrial action
Under current law, dismissal is automatically unfair if the principal reason is participation in official and protected industrial action, and the dismissal occurs during the protected period, which lasts for 12 weeks from the day the employee started participating (Trade Union and Labour Relations (Consolidation) Act 1992, s.238A). This protection applies regardless of the employee’s length of service.
A forthcoming change in the Employment Rights Bill (expected to take effect from August 2025) will remove the 12-week cap, extending protection for the full duration of the strike and after it ends. Until that change comes into force, dismissals occurring after the 12-week period may not be automatically unfair unless other legal protections apply (e.g. whistleblowing).
Dismissal protections do not apply to unofficial or unprotected action, and employees in those situations may be dismissed without recourse to unfair dismissal claims.
Legal rights of employees during official strikes
Employees involved in lawful, official industrial action have protection from dismissal as outlined above. However, current UK law does not protect employees from detriment short of dismissal (e.g. suspension, denial of bonuses, disciplinary action) for taking part in such action.
This legal gap was found to breach Article 11 of the European Convention on Human Rights in Mercer v Alternative Future Group Ltd (2022). The Employment Rights Bill will close this gap by introducing express protection against detriment, but this has not yet been enacted.
Until then, employers can lawfully impose some detriments, though they must avoid breaching implied contractual terms or triggering constructive dismissal claims.
Pay, non-union participation, and return to work
Employees are not entitled to pay for days spent on strike. Employers may withhold wages for full strike days but cannot deduct more than the actual pay lost.
Non-union members who participate in official, protected action enjoy the same protections as union members.
Employees are not required to inform their employer in advance that they will strike, but must inform them upon return to work.
Employers must keep accurate records of strike participation to correctly calculate statutory entitlements.
Effect on length of service
Strike days do not break continuity of employment, but the days do not count toward total service length. This may affect calculations for:
Statutory redundancy pay
Pension accrual
Other service-related entitlements
Once the strike concludes, continuous employment resumes as normal.
Employer and employee obligations
Employees’ pay during industrial action
Employers are not required to pay employees for any period during which they are participating in industrial action, including strikes or action short of a strike. Pay deductions should reflect only the actual time lost, and the calculation method should be consistent with the employment contract or, if silent, typically 1/260th of annual salary per strike day for full-time staff. Employers should provide advance notice of the deduction and ensure payroll records are accurate. Withholding pay for strike participation does not constitute an unlawful detriment under current law, but employers should avoid accepting partial performance unless explicitly communicated, as implied acceptance can create payment obligations for work done during partial performance.
Annual leave and strikes: employer obligations
Employees on pre-booked annual leave during a strike must be paid as normal for their leave, as they are not considered to be participating in industrial action. Employers may cancel annual leave to ensure operational needs during strikes, but must provide notice at least equivalent to the length of the leave being cancelled. If leave is cancelled, employees can choose whether to attend work or join the strike. Employers cannot require employees to take annual leave on strike days unless proper notice is given under the Working Time Regulations 1998. All changes to leave arrangements should be communicated clearly and applied consistently to avoid claims of unfair treatment.
Sick pay during strikes
Employees who are genuinely off sick during a strike are entitled to statutory or contractual sick pay, provided they comply with the employer’s sickness reporting procedures. Employers may require medical evidence from day one of absence to mitigate the risk of false sickness claims coinciding with industrial action. If there is evidence or reasonable suspicion that sick leave is being abused to avoid strike deductions, a full and fair investigation should be conducted before taking disciplinary action. Employers must not withhold sick pay solely because the absence coincides with a strike, unless there is clear evidence of misconduct.
Consequences for employers if industrial action is deemed unlawful
If industrial action is not lawfully organised—such as failures in balloting, notification, or statutory requirements—employers may seek an injunction to prevent the action from taking place or claim damages against the union, subject to statutory caps (up to £1,000,000 for the largest unions). Unions lose statutory immunity if action is unlawful, exposing them to civil claims. Employees participating in unofficial or unlawful action lose protection from unfair dismissal, allowing employers to dismiss participants without risk of unfair dismissal claims, provided dismissals are not for automatically unfair reasons (e.g., whistleblowing, health and safety). Employers should retain evidence of non-compliance to support legal remedies and ensure any action taken is proportionate and legally justified.
Resolution and mediation
Resolution and mediation in industrial disputes
Employers should attempt to resolve workplace disputes informally in the first instance, using open dialogue and negotiation with trade unions or employee representatives. Where informal efforts fail, mediation offers a voluntary, confidential process led by a neutral mediator to help parties reach a mutually acceptable solution. Mediation is particularly effective in repairing working relationships and can be used at any stage of a dispute, though it is not suitable for legal or contractual issues such as pay disputes or matters requiring formal investigation. If mediation is unsuccessful or inappropriate, formal procedures such as collective grievance processes or arbitration may be necessary. Employers are encouraged to offer mediation positively but without obligation, and should consider using external mediators where impartiality or expertise is required. Outcomes of mediation are not legally binding but can be documented and reviewed regularly to ensure ongoing compliance and relationship repair.
ACAS role in industrial action
ACAS plays a statutory and impartial role in supporting the resolution of industrial disputes, including those leading to or involving industrial action. ACAS provides conciliation, mediation, and arbitration services to help employers and unions reach agreement and avoid escalation. Early engagement with ACAS is recommended, as their involvement can facilitate constructive dialogue, clarify legal obligations, and help parties explore settlement options. ACAS can be called upon at any stage, including before, during, or after industrial action, and is highly effective in resolving disputes, with most cases reaching a positive outcome. ACAS also offers guidance on best practice, negotiation skills, and collective conciliation, and can provide external mediators or train internal staff in dispute resolution.
Guidance on picket line rules
Picketing is lawful when conducted peacefully at or near the picket’s usual place of work and for the sole purpose of obtaining or communicating information, or persuading others regarding work. The Code of Practice on Picketing recommends no more than six pickets at any entrance, and a union-appointed supervisor must be present or contactable. Pickets must not use threatening or abusive behaviour, block access, damage property, or cause a breach of the peace. Mass picketing and flying pickets (moving between workplaces) are generally unlawful. Any breach of the law or court orders can result in legal action, including injunctions and damages. Employers should monitor picketing activities and liaise with union supervisors and police as needed to ensure compliance and safety.
Guidance on collective bargaining
Collective bargaining is the process by which employers and recognised trade unions negotiate employment terms such as pay, hours, and working conditions. Employers must engage in good faith and exhaust the collective bargaining procedure before making direct offers to employees, as bypassing the union can result in significant financial penalties under s145B of the Trade Union and Labour Relations (Consolidation) Act 1992. A clear, written recognition agreement should define the scope and exhaustion of collective bargaining. Employers should document all negotiation steps, avoid making unilateral changes, and seek legal advice before declaring an impasse or communicating directly with staff. Failure to follow collective bargaining procedures can lead to tribunal claims and statutory penalties per affected employee.
