The source said the deal included Magna providing short-term financing to become the preferred bidder for GM Europe.

The German government would put up a £1.3bn bridging loan, which would be repaid when the deal was closed.

Meanwhile, union boss Tony Woodley urged the government to "get round the negotiating table and gets its cheque book out" to save Vauxhall jobs.

In a rallying call to car workers, the Merseyside-born assistant general secretary of Unite the Union said the government must be at the heart of talks to find a buyer for Vauxhall.

He said: "From early April when plans to flog off GM Europe were made public, we have been pushing our government to get round the negotiating table and get its cheque book out.

"Every one of the 5,000 workers and their families in Ellesmere Port and Luton has a roof to keep over their heads and food to put on the table.

"But it is not just the workers at the car and van plants who have worked tirelessly to turn these factories into some of the best in the world who deserve answers.

"What about the 20,000 more across the components chain, dealership and services who also rely on Vauxhall for employment?

"That means a staggering 25,000 jobs now hang by a thread."

Mr Woodley added: "We need to hear our government say that it will not allow the change in Vauxhall ownership to cost us skilled jobs.

"We need to know that when Lord Mandelson gets round the table to fight for our jobs, he has the cash he needs to deliver. Buyers will not take seriously a government which sends ministers but not money."