Cameron vows to reject €2 billion EU bill

"It is an unacceptable way for this organisation to work and an unacceptable way to treat one of the main contributors to the EU budget," he said.

"We're not going to suddenly get out our cheque book," he said, adding that "I am not going to pay this bill, it is not going to happen".

EU leaders were presented with the new calculations for national contributions to the bloc's 2015 budget on Thursday, although the figures were released to national treasuries earlier this week. However, officials were unclear about how the recalculations had been made.

Following interventions by the nine payee countries when they reconvened for talks on Friday, leaders agreed to convene an emergency meeting of finance ministers next month to resolve the row.

The calculations presented by the EU executive would require the UK to pay an additional €2.1 billion, with the Netherlands and Italy also taking hits of €640 million and €340 million respectively. Bulgaria, Cyprus, Greece, Ireland, Latvia, and Malta will also be expected to make extra payments, while nineteen will contribute less.

France and Germany would be the main beneficiaries from the recalculations, getting rebates worth €1 billion and €780 million respectively.

"This is not a figure, this is a lethal weapon," Cameron quoted Italian prime minister Matteo Renzi as telling fellow leaders.

"When people produce this lethal weapon it makes people believe that this place is full of technocrats and bureaucrats without a heart".

The bloc's GDP is nearly 2.5 percent larger than originally reported as a result of the new accounting system used by Eurostat, the EU's statistical agency, which includes sectors ranging from research and development to drug trafficking and prostitution.

A memo circulated by Eurostat on the new rules back in January stated that the new regime would have little impact on the EU budget, with national contributions "at most be affected to a minor extent".

The timing could scarcely be worse for the UK leader, whose Conservative party lost a by-election to UKIP earlier this month and is likely to lose a second seat to the anti-EU party at a poll in November.