It was the first time the bank has detailed the level of support it provided to the Royal Bank of Scotland PLC and HBOS PLC in October and November 2008, when the financial system froze in panic in the wake of the bankruptcy of Lehman Brothers.

It added that the money was paid back in full by January.

Bank of England Governor Mervyn King told lawmakers that the funding "was to prevent a loss of confidence spreading through the financial system as a whole."

'Need for secrecy'

In an additional statement, the bank said it had carefully considered the public interest case for disclosure but decided that the assistance should only be revealed "once the Bank considers that the need for secrecy has ceased."

RBS is now 84 per cent owned by the state after last year's bailout and has signed up for a government insurance plan to protect against losses on toxic assets.

HBOS was taken over by Lloyds Banking Group PLC and the combined group is now 43 per cent owned by the taxpayer. Lloyds has shunned the government's Asset Protection Scheme, announcing plans to raise capital from its shareholders instead.