European Commission President Jose Manuel Barroso has told the UK not to reverse the legend of Robin Hood by robbing poor countries to pay the rich.
Mr Barroso's spokesman urged Mr Blair to seek an "equitable" deal
His comments, reported by a spokesman, refer to the UK's unpublished plan to solve a row over the 2007-13 EU budget.
The UK is said to be proposing a cut in aid to new member states in order to reduce the overall size of the budget.
The UK was widely criticised at an EU summit in June when it blocked a budget deal by refusing to give up its rebate.
Sheriff of Nottingham
"You all know the old story of Robin Hood and the Sheriff of Nottingham. The president has made it very clear that he does not expect the British presidency to take the role of the Sheriff of Nottingham, taking from the poor to give to the rich," Commission spokesman Johannes Laitenberger told a news conference.
He added: "We are working on a fair and equitable deal where the principle should not be that those in need make the biggest sacrifices."
He added that the new member states - Cyprus, the Czech Republic, Estonia, Hungary, Latvia, Lithuania, Malta, Poland, Slovakia and Slovenia - were not among the richest in the EU.
UK Foreign Secretary Jack Straw responded: "Mr Barroso is a great man, but I think his spokesman probably knows less about what happened in Sherwood Forest than some of us."
Correspondents say the UK would give up part of its £4bn (6bn euro) annual rebate if other countries accept its latest budget proposal.
UK Prime Minister Tony Blair goes to Estonia and Hungary on Thursday and Friday to try to sell the idea to seven of the 10 new member states.
The proposal will then be discussed by EU foreign ministers on 7 December, and by heads of state and government at a summit in Brussels on 15 and 16 December.
"Whatever the deal the UK will be making a fair contribution towards the cost of enlargement and that means our contribution will in any event rise," Mr Straw said, after talks with his Italian counterpart, Gianfranco Fini, in London.
At the summit in June, the Prime Minister of Luxembourg Jean-Claude Juncker, proposed freezing the UK rebate at its current level.
The UK said it would only agree if there was fundamental reform of the EU budget, including a review of farm spending.
Mr Blair repeated on Tuesday that the rebate had to stay in place as long as "distortions" to the EU budget caused by the Common Agricultural Policy, remained.
Mr Laitenberger's comments about Robin Hood amused some reporters at the new conference in Brussels.
One British journalist asked whether Mr Barroso would approve of robbing rich French farmers loaded with large bags of grain.
Other journalists were confused. A Polish correspondent asked Mr Laitenberger for more information about the role played by the Sheriff of Nottingham.