Unions have joined forces to mount a legal challenge against the government's "strike-breaking" agency worker regulations.
Accusing ministers of attacking the right to strike in "broad daylight", The Trade Union Congress (TUC) is launching a judicial review on behalf of 11 unions.
Collectively they represent millions of workers, including train drivers, civil servants, shop workers, and prison officers.
It comes after the government unveiled a new law in July that allows businesses impacted by industrial action to plug staffing gaps at short notice with skilled agency workers.
The measures came in response to a series of strikes over the summer by members of the Rail, Maritime and Transport Workers' union, who had walked out in a dispute over pay and working conditions.
The then Business Secretary Kwasi Kwarteng said: "In light of militant trade union action threatening to bring vital services to a standstill, we have moved at speed to repeal those burdensome, 1970-style restrictions''.
Coordinated by the Trade Union Congress (TUC) the legal action announced today centres on the claim Mr Kwarteng failed to consult union leaders over the plans.
The TUC also claims the regulations violate fundamental trade union rights protected by Article 11 of the European Convention on Human Rights.
It warns the new law will worsen industrial disputes, undermine the fundamental right to strike and could endanger public safety if agency staff are required to fill safety critical roles but have not been fully trained.
TUC general secretary France O'Grady said: "The right to strike is a fundamental British liberty. But the government is attacking it in broad daylight.
"Threatening this right tilts the balance of power too far towards employers. It means workers can't stand up for decent services and safety at work - or defend their jobs and pay."
She claimed: "Ministers failed to consult with unions, as the law requires. And restricting the freedom to strike is a breach of international law. That's why unions are coming together to challenge this change in the courts".
Richard Arthur, Head of Trade Union Law at Thompsons Solicitors LLP, said: “The right to strike is respected and protected by international law including the Conventions of the ILO, an agency of the United Nations, and the European Convention on Human Rights.
“The Conservative government should face up to its legal obligations under both domestic and international law, instead of forever trying to undermine the internationally recognised right to strike.”
The Department for Business, Energy & Industrial Strategy has been contacted for comment.
