Crisis could double Britain's debt

The surge has been fuelled by huge liabilities dumped on the public balance sheet by the Royal Bank of Scotland (RBS) and Lloyds Banking Group's.

But the figure - at the top end of initial ONS estimates - is based on an assumption that all risky loans will go bad, so that the Treasury can prepare for such a worst-case scenario.

Also, under the asset protection scheme which insures loans that turn sour, banks are liable for the first £60 billion before the taxpayer becomes responsible for losses.

Nonetheless, the figure of £2.3tr is colossal and was announced just as RBS, which has risky loans totalling £282bn, revealed it had already eaten into £30bn of the money it is liable for - increasing the likelihood that the taxpayer will have to pay off the remaining £222bn.

This gloomy picture was made worse by RBS unveiling a pre-tax loss of £2.1bn in the July to September period and the announcement that 3,700 front-office jobs are lined up to be axed.

This was on top of the 4,500 back-office cuts announced in April.

Following these developments, RBS chief executive Stephen Hester said the bank was "more than halfway through" its major restructuring programme.