Workers who face losing their jobs at Peugeot's factory near Coventry have taken their protests to London.
Workers have been told the plant will close in July next year
Union members have also demonstrated in Coventry and Birmingham about the planned closure at Ryton in July with the loss of 2,300 jobs.
On Monday, staff joined the traditional May Day trade union rally to gain more support for their campaign.
Trade Union Congress general secretary Brendan Barber called for stronger employment laws at the rally.
Tony Johnson, a Peugeot worker who made the journey said: "We've got to fight and we're not going away. This plant is doing the best, delivering the best what more can you ask for?"
Des Quinn a Transport and General Workers' Union regional organiser, who also made the trip from Coventry, told the BBC: "If you fight you don't always win, but if you don't fight you will surely lose."
Addressing the rally, Derek Simpson, Amicus general secretary, warned the government it risks defeat at the next general election.
"The sooner this government learns some humility, starts listening to ordinary people, does something about employment laws, does something about pensions, does something to protect industry, then this demonstration would have served its purpose."
He said the last week alone provided a snapshot of what was happening up and down the country with closures and job cuts announced at Peugeot, TVR and Prudential.
At Ryton, the unions have drawn up a business plan that would keep the plant open.
Workers staged a protest outside a Coventry dealership on Friday and handed out leaflets in Birmingham on Saturday outlining their alternative plans.
The unions' proposal would prevent the closure and include moving to a single production shift this summer to allow workers to leave if they wanted to.
A new model would be built at Ryton in 2009/10, when the factory would operate on up to four shifts, the unions suggested.