The UK's largest union, UNISON, has sent a pre-action letter to the Business Secretary, Kwasi Kwarteng, over a recent change to the law that allows employers to use agency workers to replace striking staff during industrial disputes.
UNISON, which represents staff in public services, claims that last week's change to the Conduct of Employment Agencies and Employment Business Regulations 2003 was based on a seven-year-old consultation and flawed evidence.
The union also alleges that the Government is in breach of Article 11 of the European Convention on Human Rights, which protects the right to strike and international labour standards.
On 20 July 2022, the Government amended the Regulations to omit provisions which put restrictions on businesses on providing work-seekers in industrial disputes.
UNISON has more than 1.3 million members, making it the largest in the UK.
A spokesperson for the union said: "The hope is still that the Business Secretary will have a change of heart, but recent rhetoric from ministers suggests this is unlikely.
"Instead of making it harder for ordinary working people to go on strike, the government should be talking to unions and employers about how to solve the cost-of-living crisis together."
A government spokesperson said: "The Business Secretary makes no apology for taking action so that essential services are run as effectively as possible, ensuring the British public don't have to pay the price for disproportionate strike action."