The Deputy Prime Minister John Prescott has urged Jaguar's parent company Ford to reconsider cutting 1,150 jobs.
Unions claim promises have been broken over the Coventry plant
Jaguar workers are lobbying the Labour Party conference in Brighton as part of a campaign to fight the decision to stop making cars in Coventry.
Ford recently announced proposals to switch production from the Browns Lane plant to Castle Bromwich, Birmingham.
Mr Prescott, who has one Jaguar for his personal use and a Government one, said production must remain in this country.
Speaking on the day he met workers from Coventry at the party conference, he also accused the company of going back on a promise.
Unions say Ford had previously signed agreements with the workforce guaranteeing a secure future for the West Midlands plants, ongoing investment and a new model for production in 2006.
Mr Prescott said: "These are quality cars built, produced and designed here in Britain. We want to make sure they continue to be built, produced and designed here.
"I have got one car and I have got this car, a Government car, and I am damn proud of them.
"We should always be about excellence and this is the mark of excellence."
The restructuring plans will lead to 1,150 job losses across the company and unions have warned of industrial action.
Amicus and the Transport and General Workers' Union will move an emergency motion this week urging the government to introduce stronger protection for UK workers.
Jaguar cars are currently made at three sites in the UK and all have been producing at less than capacity. The other two plants are at Castle Bromwich in the West Midlands and Halewood on Merseyside.
Some industry analysts have recently argued they should be made at one central plant instead, possibly outside the UK.