The European Commission president has defended the £1.7bn surcharge imposed on Britain after David Cameron insisted the money will not be paid by December 1.

The increase would add almost a fifth to the UK's annual contribution of £8.6bn .

The Prime Minster, who has called an emergency meeting with EU finance chiefs, told a news conference in Brussels: "This is completely unacceptable.

"It is an unacceptable way for this organisation to work to suddenly present a bill like this for such a vast sum of money, with so little time to pay it and it's an unacceptable way to treat one of the biggest contributors to the European Union.

"Of course in an organisation like this, if your economy grows a little faster or ... slower, there are adjustments. Sometimes you pay a little bit more, sometimes you play a little bit less.

"I'm not paying that bill on the 1st of December and if people think I am, they've got another thing coming. It is not going to happen.

"As an important contributor to this organisation, we are not suddenly going to get out our chequebook and write a cheque for 2bn euros. It is not happening."

Outgoing Commission president Jose Manuel Barroso insisted Brussels was only following the procedures created by member states to balance the EU's books each year.

Mr Barroso told reporters the figure of £1.7bn had been calculated by the independent Eurostat organisation using statistics provided the 28 member states.

"Of course, I understand the concerns it has raised in London, but any person that wants to look with objectivity and honesty at the rules that were approved by the member states has to accept that sometimes these decisions happen," he said.

Asked how the Commission would respond if Mr Cameron made good on his threat to withhold payment, Mr Barroso replied: "I can't now speculate on non-payment."

Earlier, Commission spokesperson Patrizio Fiorilli said the surcharge was fair because it was like personal taxation - the more a person earns, the more they have to pay.

Mr Fiorilli said: "Britain's contribution reflects an increase in wealth, just as in Britain you pay more to the Inland Revenue if your earnings go up."

The demand is the result of improvements to Britain's economy since 1995.

Preliminary figures seen by the Financial Times suggest Britain is facing the largest adjustment in the amount it must pay compared to other member states.

The Netherlands is being asked for an extra £509m, but by contrast France is due to receive a rebate of £0.8bn, Germany £618m, and Poland £250m.

Britain's surcharge is due for payment on 1 December - just days after the Rochester and Strood by-election, which hangs on a knife edge with anti-EU UKIP threatening to wrest the seat from the Tories.

Several Conservative MEPs have spoken out against the surcharge, saying Britain is being punished for its success.

UKIP leader Nigel Farage told Sky News: "It just leaves Mr Cameron in a hopeless condition, because don't forget, one of his big claims was he'd cut the EU budget."