Opponents have attacked the deal reached by Tony Blair on the EU budget as a "spectacular failure" and disappointing end to the UK presidency.
Foreign affairs spokesmen for both the Tories and Liberal Democrats criticised the agreement made overnight.
Mr Blair has defended the deal, which cuts the annual rebate by £1bn a year.
He said it would ensure new EU states got the development money they needed, and put UK contributions on a par with nations like France for the first time.
The rebate remained on all other expenditure and would rise, not fall, due to an overall spending increase for the budget from 2007 to 2013, he added.
The prime minister argued that the agreement - which covers the EU's budget for seven years from 2007 - also allows Europe to "move forward".
But shadow foreign secretary William Hague said although his party agreed with some of the government's aims it should have won assurances in return for its sacrifice.
"The government has spectacularly failed to achieve any such guarantees - merely vague promises of a process of reform in the future, in exchange for which they have surrendered £7bn in Britain's rebate alone. Those vague promises have come with a very high price tag.
"Seldom in the course of European negotiations has so much been surrendered for so little," he said.
Meanwhile Liberal Democrat spokesman, Sir Menzies Campbell, said the deal marked a "thoroughly disappointing" end to the UK's six-month presidency of the EU.
"Government tactics have resulted in a reduced rebate but no real progress on Common Agricultural Policy reform," Mr Campbell said.
European leaders agreed the budget plan after two days of what Mr Blair described as "extraordinarily complicated" talks.
BBC Europe correspondent Tim Franks said the rebate would continue to rise "for a time" because Britain's overall contributions were rising.
They will increase by 63% to £42bn, while French contributions will rise by 116% and those of Italy by 130%.
Britain is giving up around 20% of the rebate it would have otherwise received over the seven years.
Although it will rise from its current level, it will be smaller as a proportion of the UK's net contribution to the EU.
The prime minister told BBC Radio 4's Today programme that for the first time Britain's net pay-in was roughly on parity with France.
"So when people talk about the money that Britain's putting in, it's almost as if Britain was putting money in but no-one else was," he said.
Push for reform
The budget package is worth £584bn (862bn euros) - an increase on the £575bn (849bn euros) limit Mr Blair originally proposed.
The UK gives up £7bn (10.5bn euros) of its rebate, after initially offering £5.5bn (8bn euros).
It was agreed the EU would review all its spending in 2008-2009, including the Common Agricultural Policy (CAP), which Mr Blair wants to see reformed as part of a "start from the very beginning" negotiation.
UK Independence Party MEP Nigel Farage said the CAP would not change until 2014, which was what President Chirac set out to achieve.
"Do British taxpayers really want to pay for new sewers in Budapest or a new underground system in Warsaw? I suspect not," he told the BBC.
Speaking from Brussels Mr Blair said it was never his position that those fundamental reforms could be agreed now.
"My case is that you have to ensure that the enlargement can go ahead - and that's the reason for Britain paying its fair share for the cost of economic development."
But he added there was no question of the rebate being given up until there was a fundamental budget restructuring, and that the deal had put in place a process to allow such reform.