Germany will demand that other European countries including the UK contribute almost half the €4.5bn in loans it has pledged to fund Magna's takeover of Opel/Vauxhall, British government officials have warned.

Berlin had promised to underwrite the entire cost of Magna's plan to restructure Opel/Vauxhall to protect German jobs ahead of elections later this month. But officials say Germany will seek to offload 30–40% of the loans – up to €1.8bn – to other European countries, even though the car group's workers, including the 5,500 Vauxhall employees in the UK, stand to lose out under the Magna plan.

In meetings between government officials last week, the Germans asked their European counterparts to share the risk of financing a restructured Opel/Vauxhall. But according to one source, they received "lots of push back" as the UK and others questioned the commercial logic of the deal and who it would benefit. Magna, backed by Berlin, is also understood to be making "ambitious" demands over the amount of financial support it expects from the government.

Business secretary Lord Mandelson has indicated that he will provide up to £400m in aid to Magna provided it can demonstrate it has a viable business plan which retains as many jobs in the UK as can be commercially justified. However, officials believe that "fundamental" questions remain about the viability of Magna's plan, which would avoid closing any of Germany's plants. Magna will be asked to justify why British taxpayers' money should be put at risk if it is not commercially viable.

There is concern that Magna is envisaging a far higher break-even figure for the business than in plans put forward by private equity group RHJ and parent company GM. Under Magna, Opel/Vauxhall's costs would be much higher, because it would retain more inefficient production capacity in Germany, and because of its huge borrowing costs.

Magna's plan involves borrowing €4.5bn from governments, while RHJ only asked for €3.2bn. Magna chief executive Sigi Wolf said last week that the consortium, which includes Russian partner Sberbank, would be charged double-digit interest rates for the loans.

Opel/Vauxhall employs 50,000 people in Europe, with half in Germany. Other countries with Opel/Vauxhall operations – the UK, Spain, Poland and Belgium – are concerned that Berlin's support is driven by political, as opposed to commercial considerations.

The European commission has said it will scrutinise the deal and Mandelson has urged regulators to act against anything that "looks like a political fix".

Magna has committed to the future of Vauxhall's two plants in the UK, at Ellesmere Port in Merseyside and Luton. But up to 2,000 jobs could be lost if, as planned, Magna reduces capacity at Ellesmere and closes Luton when a joint venture with Renault ends in 2013.