Sberbank, Vauxhall's new part-owner, is the Big Daddy of Russian banks, practically an extension of the state budget in implementing the Kremlin's industrial policies.

Russia's Central Bank controls 60 per cent of the voting shares and Sberbank's chief executive is German Gref, who was Economic Development Minister. Sberbank accounts for a third of Russia's banking capital and is the biggest of three state-controlled banks that have been used to funnel billions of dollars in liquidity to Russia's financial markets during an economic crisis that has hit the value of companies owned by oligarchs such as Oleg Deripaska.

Mr Deripaska owns Gaz, Russia's second-largest carmaker, saved from bankruptcy after Vladimir Putin, the Prime Minister, put £600 million in state aid into the car industry in April. The Government had declared Gaz too big to fail and Sberbank is owed most of the company's £900 million debt.

Gaz considered a partnership with General Motors last year, before the financial crisis, to make a budget car in Russia. Now it operates at 30 per cent of capacity, with thousands laid off.

Mr Deripaska bought a 10 per cent stake in Magna in 2007 but in October had to hand it to the bank that financed the deal after facing a margin call from BNP Paribas, the French bank. His alliance with the Canadian car parts maker was seen as an attempt to inject Western expertise into modernising Gaz.

The plan to make Opel cars at a Gaz plant in Russia lets him achieve that goal another way. Russian Machines, Gaz's majority shareholder and part of Mr Deripaska's Basic Element, is on a Kremlin list of strategically important companies eligible for preferential access to state loans.

Sberbank's involvement in the Opel takeover indicates strong Kremlin backing as part of Mr Putin's strategy of making European Union states more dependent on Russia, to blunt criticism of its foreign policy and human rights record.

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