After the complex rebate system is taken into account, British taxpayers will have to pay around £350 million more.

Chris Heaton-Harris, the Conservative MP for Daventry and co-founder of the Fresh Start group of Euro-sceptics, said: "The case for reform is greater now than it has ever been.

"We are just about to increase the EU budget, and our part of that increase is £350 million.

"That would pay a year’s basic salary to at least 18,500 Army privates, the average basic salary to more than 10,500 NHS-qualified nurses, or a year’s basic salary to around 12,500 police constables.”

David Nuttall, the MP for Bury North, said: “At a time when we are cutting our budgets here in the UK, the fact is that, whatever happens in the negotiations, those in Europe and Brussels want the European budgets to be increased. Meanwhile, my constituents are seeing their budgets being cut.”

Many Tory Euro-sceptics believe the extra funding for the EU is particularly unpopular because it comes at a time when its institutions are earmarking taxpayers’ cash for costly projects.

A new EU HQ – the Konrad Adenauer centre in Luxembourg – will cost £350 million, the exact size of the likely increase in the extra funding Britain will provide for the EU next year.

Housing 2,000 staff, it will include restaurants, a gym, the latest green technology and a so-called “majestic entry portal” built on 16 steel pylons.

Mr Hoban said Britain had identified many areas of EU spending that were ripe for reform.

“It is time to cut the quangos, EU staff pay and programmes that offer low value or are poorly implemented,” he added.

The total salary bill for staff at EU institutions in 2011 was more than £2.7 billion, which is more than double the amount it spends on freedom, security, justice and citizenship.

Many staff get an extra 16 per cent “expat” allowance on top of their salaries.

The European Commission originally proposed a 6.8 per cent increase in EU spending for next year – but this was beaten down during lengthy negotiations among national governments.

Earlier this month the “compromise” 2.8 per cent increase was agreed in principle despite Britain’s opposition.

Anything bigger would have been blocked by bigger countries which are “net contributors” to the EU’s budget, including Germany and France.

A smaller increase, however, would have been blocked by an alliance of poorer countries which are “net recipients.”

Britain is the second biggest net contributor to the EU after Germany, ahead of France and Italy.

The focus will next shift to negotiations for the next “financial framework” which will set overarching totals for spending to cover the period from 2014 to 2020 – with the backdrop of the continuing eurozone crisis.

Growing numbers of Conservative and Labour MPs are supporting moves for wealthier countries to be able to “repatriate” structural funds – money used on projects designed to cut the gap between rich and poor across the EU – during the new financial framework period. This could save the UK billions of pounds.

Mats Person, director of the Open Europe think tank, said: “That the UK government risks being outvoted on the 2013 EU budget shows how incredibly important it is to get the EU’s long-term budget – over which the UK has a veto – right.

“To avoid this scenario again, in the ongoing talks over the 2014-2020 EU budget, the UK government must not only push for a freeze but for a fundamental refocusing and reduction of EU spending – and be prepared to use the veto should this not happen.

"The best place to start would be to repatriate EU regional spending to the UK and other wealthier member states. This would save UK taxpayers billions and give Cameron instant credibility on Europe.”