Can Employers Penalise Strike Action?

27th April 2026

Lucy Harwood

What the Supreme Court’s Ruling in Mercer Means for Workers and Employers

Secretary of State for Business and Trade v Mercer [2024] UKSC 12

Can Your Employer Punish You for Going on Strike?

In a significant decision in April 2024 (following earlier appellate consideration in 2022), the UK Supreme Court held that a provision of employment legislation was incompatible with workers’ human rights. The case, Secretary of State for Business and Trade v Mercer [2024] UKSC 12, clarified the limits of statutory protection for workers taking part in lawful industrial action.

The decision has informed employer practice in relation to industrial action and remains relevant as Parliament continues to develop the statutory framework in this area, particularly for those managing unionised workforces or industrial disputes.

Whether you’re a manager, HR professional, or business owner, this decision is important in understanding how far legal protections extend during industrial action. This summary explains the background, the reasoning and the practical implications.

What Happened?

Fiona Mercer was a support worker in the care sector, employed by Alternative Futures Group Ltd (AFG), and also acted as a UNISON workplace representative. In early 2019, UNISON organised industrial action relating to changes to sleep-in shift payments. Ms Mercer was involved in supporting and communicating about the dispute and indicated she intended to participate in strike action.

On 26 March 2019, her employer suspended her for nearly two weeks and subsequently issued her with a first written warning alleging misconduct in relation to her conduct at work. During the suspension, she received basic contractual pay, but did not receive additional earnings she would otherwise have received, resulting in financial loss.

She argued that the suspension and disciplinary action amounted to detrimental treatment because of her involvement in trade union activities and participation in industrial action.

What Claims Were Brought and How Did the Courts Decide?

Ms Mercer brought a claim under section 146 of the Trade Union and Labour Relations (Consolidation) Act 1992 (TULRCA), which protects workers from suffering detriment for taking part in trade union activities ‘at an appropriate time’.

However, the central issue was the established interpretation of section 146.UK courts had previously held that participating in industrial action did not fall within the scope of ‘trade union activities’ for the purposes of that provision.

This created a gap in protection. While the Employment Rights Act 1996 (ERA) provides limited protection against dismissal in the context of lawful industrial action,, there was no general statutory protection against detriments short of dismissal, such as suspension, demotion, or disciplinary action linked to participation in strike action.

The case proceeded through the courts as follows:

The Employment Tribunal held that s.146 did not apply to participation in industrial action.

The Employment Appeal Tribunal held that s.146 could be interpreted compatibly with Article 11 of the European Convention on Human Rights (ECHR), applying s.3 of the Human Rights Act 1998 (the duty to interpret legislation compatibly with Convention rights, so far as possible)..

The Court of Appeal disagreed, holding that such an interpretation was not possible and declining to make a declaration of incompatibility.

The Supreme Court ultimately held that s.146, on its proper construction, was incompatible with Article 11 ECHR insofar as it failed to protect workers from detriment short of dismissal imposed for participation in lawful industrial action. A declaration of incompatibility was made under s.4 of the Human Rights Act 1998.

Article 11 ECHR protects the right to freedom of assembly and association, which includes trade union membership and participation in collective action, including strike action as recognised in case law. However, the Court confirmed that this right is not absolute, and states retain a margin of discretion in regulating industrial relations.

What Does This Mean In Practice?

This was not a damages-based claim, but a constitutional challenge. The result was a declaration that s.146 TULRCA is incompatible with Article 11 ECHR

The legislation remains in force unless and until Parliament chooses to amend it. In response to the issues identified in Mercer, legislative reforms under the Employment Rights Act 2025 have since been introduced to strengthen protection for workers participating in industrial action, although the precise scope and operation of those changes continues to evolve.

More broadly, the case confirms that industrial relations engage Article 11 ECHR considerations and must be approached within that rights-based framework, rather than purely as operational workforce management.

Top 5 Lessons for Employers

Review your suspension and disciplinary processes during industrial action. If your current policies allow for suspension or disciplinary action to be taken against employees who participate in lawful strikes they should be carefully reviewed to ensure they do not create a risk of detriment linked to participation in lawful industrial action. The Supreme Court’s reasoning in Mercer highlights the legal sensitivity of such decisions under Article 11 ECHR..

Train managers on industrial action risks. Many line managers are unaware of the legal boundaries during industrial disputes. A manager who suspends or disciplines a striking employee, even with the best intentions around operational continuity, could expose the organisation to risk. Training is a practical risk-management tool, particularly where decisions may intersect with statutory protections and human rights considerations during industrial action..

Avoid detriment linked to industrial action. Never use detriment as a deterrent The core issue in Mercer was that the employer’s actions appeared to be designed to discourage trade union activity, including strike participation. Using threats, disciplinary processes, or financial penalties to deter workers from exercising their legal rights is not just poor employment practice, it engages Article 11 ECHR considerations and may give rise to unlawful detriment claims depending on the statutory framework and facts of the case.

Engage early and constructively with trade unions. Many industrial disputes escalate because employers and unions fail to communicate effectively at an early stage. Building a positive and constructive relationship with union representatives in normal times makes it far easier to manage disputes when they arise.

Monitor legislative developments (including ERA 25 reforms). The declaration of incompatibility means Parliament is now under pressure to amend s.146 TULRCA. The declaration of incompatibility has prompted ongoing reform activity under the ERA 25. These reforms are intended to strengthen protections in the context of industrial action, although the precise scope and implementation remain subject to legislative development and commencement provisions. Ensure your HR and legal advisers are monitoring developments so you can adapt your policies swiftly.

How Can Thrive Law Help?

At Thrive Law, we specialise in employment law that puts people first, supporting both employers and employees to understand their rights and responsibilities clearly, practically, and without jargon.

Following this Supreme Court ruling, we can help you:

Conduct a review of your industrial action policies and procedures.

Deliver bespoke training for managers and HR teams on handling industrial disputes lawfully and sensitively.

Advise on your organisation’s obligations under the Human Rights Act in employment contexts.

Support you in building constructive relationships with trade unions and employee representatives.

Provide legal advice if a dispute or employment tribunal claim arises.

Whether you’re an employer wanting to get ahead of the curve, or a worker who believes their rights have been infringed, we are here to help.

Final Thoughts

The Mercer case is a significant decision in UK employment law. It confirms that statutory protection for participation in lawful industrial action is not complete and must be understood within the limits of the current legislative framework and Article 11 ECHR..

For employers, the message is practical: industrial action is not a battleground but a regulated aspect of the employment relationship governed by statutory and Convention rights, and workers who take part in it lawfully are protected to the extent provided by law. The law is continuing to evolve through both case law and legislative reform, including developments under the ERA 25. Employers who engage early with these developments will be better placed to manage risk than those who take a reactive approach.

At Thrive Law, we believe that thriving workplaces are built on respect, fairness, and clear communication. This case is a reminder of the importance of ensuring that industrial relations are managed carefully, lawfully, and with a clear understanding of employees’ statutory and human rights protections.

Get in touch: If you have questions about how this ruling affects your business, or if you need support reviewing your industrial action policies, contact Thrive Law today.

References

Read the full Supreme Court judgment: [2024] UKSC 12

Read the press summary: UK Supreme Court Press Summary

Secretary of State for Business and Trade v Mercer [2024] UKSC 12, [2024] 4 All ER 1, [2024] IRLR 599, [2024] ICR 814, 57 BHRC 113, [2024] All ER (D) 64 (Apr)