Unite the Union joint general secretary Derek Simpson said: “Thousands of jobs are at stake at Luton and Ellesmere Port.

“Once lost, they won't return, our manufacturing capability and the UK's research and development base will be left hamstrung.

“This is crunch time. “Yesterday, with the clock ticking on a rescue deal, joint general secretary at Unite, Merseyside-born Tony Woodley, demanded Lord Mandelson get on a plane and fly out to Germany to put the UK’s case for funding and support for Vauxhall jobs.

Last night the minister responded by saying he had flown to Belgium to meet one of the major shareholders of Belgium-based private equity group Ripplewood Holdings.

Loan guarantees to the successful bidder may also be available, if Vauxhall need it.

But with pledges of up to £6.2bn in state aid for the new owner to support four car plants in Germany and half GM Europe’s 25,000-strong workforce, there are fears the German government could give in to election-year pressure by protecting their jobs at the expense of UK plants. The Berlin government is expected to announce its preferred choice today.