A protest is being held on Monday against the Government’s controversial legislation on minimum levels of service during strikes, which unions warn could lead to workers being sacked for legally voting to take industrial action.

Union leaders involved in the current wave of strikes will speak at the event in Parliament Square and will criticise the Strikes (Minimum Service Levels) Bill, which returns to Parliament for MPs to discuss amendments put forward by the Lords.

The TUC has warned that the right to strike of one in five workers is at risk, as the Bill means that when workers lawfully vote to strike in health, education, fire, transport, border security and nuclear decommissioning, they could be forced to attend work and sacked if they do not comply.

The TUC said MPs have been given few details on how minimum service levels will operate, adding that the legislation has faced a “barrage” of criticism, including from employer groups.

TUC general secretary Paul Nowak told the PA news agency that Conservative MPs should “vote with their conscience” and oppose the Bill.

It’s no surprise that politicians, employers and rights groups are queuing to condemn this spiteful Bill

He warned that the legislation would worsen industrial relations and prolong strikes.

“Do MPs really want to see teachers, nurses or railway workers sacked for taking lawful industrial action?

“This draconian legislation is a step too far.

“It’s undemocratic, unworkable and if it gets onto the statute book very likely unlawful, and it will poison industrial relations and exacerbate disputes rather than help resolve them.

“It’s no surprise that politicians, employers and rights groups are queuing to condemn this spiteful Bill.”

Mr Nowak said the TUC will explore “every possibility” of mounting a legal challenge to the legislation when it becomes law.

“Ministers must step back from the brink, ditch this draconian Bill for good and protect the right to strike.”

He warned of a “huge reaction” if and when the first worker is sacked under the legislation.

Labour has promised to repeal the Bill if it wins the next general election.

The House of Lords put forward a number of amendments, including ensuring that failure to comply with a so-called work notice under the legislation was not a breach of contract so a worker could not be sacked.

The Lords also want an amendment that unions do not have any responsibility or obligation to ensure their members comply with a work notice.

Speakers at the protest will include Mr Nowak and Mick Lynch, general secretary of the Rail, Maritime and Transport union, which has been embroiled in a long-running dispute over pay, jobs and conditions.

Fire Brigades Union general secretary Matt Wrack said: “The UK already has the most restrictive anti-union laws in the developed world and the result of this is that we have suffered from falling wages and sharper exploitation.

“An inspiring wave of resistance has swept the country in the past year, but instead of negotiating with workers, this Government of millionaires is seeking to have key workers sacked and victimised. They want to drive wages down even further so their big business backers can cash in.

“There is a growing movement of resistance to this legislation and the FBU is committed to building a mass movement of non-compliance if it becomes law.

“We are seeing a workers’ revolt against hard-right government with no mandate for its policies. That revolt will continue whatever happens today.”