Taxpayers could face a multimillion-pound bill for the rescue of Northern Rock, after Alistair Darling refused to give a guarantee that the £24 billion Bank of England loan will ever be fully repaid.

Mr Darling was told that his job was on the line yesterday in acrimonious scenes in the House of Commons, when he was accused of reneging on clear promises.

Under questioning in the Commons, the Chancellor insisted that the Government “fully expected” to get back the £24 billion that the Bank of England had lent to the troubled bank because the money was secured against its assets.

But he did not answer when both George Osborne, the Shadow Chancellor, and Vince Cable, the acting Liberal Democrat leader, asked him to guarantee that the loans plus interest would be repaid in full. Opposition spokesmen claimed that Mr Darling’s assurance was weaker than those previously given by the Government, and said that the Treasury’s statement to the Stock Exchange, that it would expect the private sector “to the greatest extent possible” to bear the costs, was open to doubt.

Mr Osborne said that the “fallout from the first bank run in 141 years gets worse each week” and accused the Chancellor of “another day of weakness and confusion”.

He demanded: “The question we now ask of you is simple. Have you been honest with taxpayers about the risks they face and have you told the whole truth?”

Mr Osborne said MPs would hope that when the final reckoning came the taxpayer had not paid a heavy price.

“We have a Chancellor who has made guarantees to the taxpayer he cannot be sure of honouring. And we have a Chancellor whose weakness is contributing to the instability of the financial system. That is why we have a Chancellor whose job is on the line.” Earlier, he told the BBC Radio 4 Today programme: “Alistair Darling made a clear promise that taxpayers’ money would be protected, that taxpayers would get their money back. He made that in Parliament when he spoke to the select committee.”

But it emerged last night that Mr Darling would consider all options for the Bank — including a form of public ownership — if the various deals now under consideration meant that the taxpayer would lose significant sums of money.

An informed source told The Times: “Nothing, including nationalisation, is ruled out. We cannot allow the taxpayer to make significant losses on this.”

However, officials admitted that the Treasury would not necessarily have first call on a sum of about £50 million due to be paid back by Northern Rock in February because of a “penalty” it had incurred for being allowed to borrow from the Bank at the base rate rather than a commercial rate. Mr Cable said: “Tony Blair was widely criticised for advancing £800 million for the Millennium Dome. In the last few weeks this Government has provided the equivalent of 30 Millennium Domes to this bank without even the prospect of a decent pop concert at the end of it.”

The political divisions over Northern Rock intensified on the day the company said that the bids received from potential investors were “materially below” its share price.

Two suitors, Virgin Group and Olivant Advisers, have submitted proposals to rescue the bank. But news of their valuations sent Northern Rock shares plunging by 2 per cent to a record low by yesterday afternoon. The Newcastle upon Tyne-based bank, which employs about 6,000 staff, said that it expected to receive further expressions of interest over the next few days.

As well as Virgin and Olivant — an investment company headed by Luqman Arnold, the former Abbey boss — the private equity companies JC Flowers and Cerberus have eyed the Rock. The bank, whose chief executive, Adam Applegarth. resigned on Friday, said that while it would still analyse and discuss proposals it had received “the value to shareholders from any of the proposals remained highly uncertain”.

Mr Darling told the Commons that the Government would consider sale proposals with a view to “reaching the best outcome for the public purse”.

It would “only support a proposal that protects the interest of the depositors and the taxpayers”.

He added: “It is in the interests of everyone that the situation is resolved as soon as possible. It would be quite wrong to dismiss any option now without proper consideration as some suggest.” He added that savers’ deposits would continue to be guaranteed, and that if the situation was set to change plenty of notice would be given.

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