Britain looks set to be asked to commit more money to the International Monetary Fund, after the global organisation confirmed it was planning to raise an additional 500 billion US dollars to shore up ailing economies.
The announcement sparked warnings of a possible rebellion by Government backbenchers unhappy at the prospect of British taxpayers being asked to underwrite lending to eurozone countries struggling to cope with their debts.
The UK is currently liable for 4.5% of the IMF's 400 billion dollar lending capacity, leading to speculation that the planned increase would mean an additional British liability of around £17 billion.
But Treasury sources said it would be misleading to put a figure on any possible additional contribution, stressing that talks were only at a preliminary stage and the IMF had put no firm proposals on the table.
Parliament has already approved around £40 billion in support for the IMF, of which about £30 billion is committed. Any new request going beyond the £10 billion "headroom" available to Chancellor George Osborne would have to be approved by MPs.
Downing Street confirmed that Mr Osborne was ready to put any "decent" request from the IMF to MPs.
But Prime Minister David Cameron made clear that any increase in UK funding would have to be designed to assist struggling countries and not to bail-out the euro.
Speaking at 10 Downing Street following talks with Italian Prime Minister Mario Monti, Mr Cameron said: "We are founder members and great supporters of the IMF. It's a key international institution.
"We set out our conditions at the Cannes G20 summit about expansion of the IMF. We believe the IMF must always lend to countries, not to currencies. We would only act if that was with others, not just as part of a eurozone measure.
"But above all, we want to see that the eurozone is standing behind its own currency. The case has to be looked at in that context, but we are founder members of the IMF and strong supporters of it."
