Britain will not pay "anything like" the £1.7 billion which is being demanded by the European Commission in additional contributions to the EU budget, Prime Minister David Cameron has told MPs.
In a statement to the House of Commons, Mr Cameron made clear that he believes the row triggered by last week's request for more cash is undermining support for British membership of the EU, and warned that Brussels must change if it is to regain taxpayers' trust.
But the Prime Minister was accused of being "asleep at the wheel" by Labour leader Ed Miliband.
He said Mr Cameron should have been aware for at least two years that changes to Britain's contribution to the EU budget were in the offing.
Tory MP Kenneth Clarke - until July a member of Mr Cameron's Cabinet - cast doubt on the Prime Minister's claim that the demand took the Government by surprise, telling MPs that the Foreign Office and Treasury must have known for at least five months it was on its way. Mr Cameron's statement came shortly after a senior Brussels official warned that British efforts to renegotiate the figure risked opening a "Pandora's box" which could put the future of the UK's £3bn-a-year EU rebate in question.
Budget commissioner Jacek Dominik said it would be "extremely difficult" for the UK to challenge the demand, as any change would require securing the support of a qualified majority of member states for amendments to EU law.
Mr Dominik warned that the UK was obliged by law to pay by December 1 and would be liable for "late payment fines" if it failed to hand over the cash - which reflects changes in the relative national income of different EU states - on time.
Mr Cameron told the Commons: "Britain will not be paying two billion euros to anyone on December 1 and we reject this scale of payment.
"We will be challenging this in every way possible. We want to check on the way the statistics were arrived at, the methodology that was used. We will crawl through this in exhaustive detail."
And he told MPs: "We are not paying two billion on December 1 and we are not paying a sum anything like that. That is very clear.
"When your economy grows, you pay a bit more. When your economy shrinks, you pay a bit less. But what is not acceptable is a two billion euro bill and we won't be paying it."
Mr Cameron told MPs: "The EU has to change. It has to regain trust."
Britain is by far the biggest loser in the EU recalculation, while some other major states stand to benefit to the tune of hundreds of millions of euros - with France expecting €1bn (£800m) and Germany €779m (£614m).
Mr Cameron said it was "perverse" that some poorer countries like Greece should be asked to pay money to Germany.