The European Parliament has demanded further negotiations on the EU's multi-year budget, after national leaders agreed to a cut of 3.3%, reports the BBC.
Euro MPs adopted a resolution saying they would only accept the deal on certain conditions.
They want governments to settle outstanding budget bills, to avoid the risk of a shortfall.
The MEPs also want a flexible 2014-2020 budget, so that money not spent in one area can be used in another if needed.
The deal was reached by EU leaders in February at their second attempt, after a battle between countries which wanted their EU contributions to fall in line with national austerity cuts, and others which wanted to see EU spending maintained or boosted.
Many MEPs, along with the European Commission, fell into the second category.
"Today's vote is a clear indication that the European Parliament has accepted the responsibilities given to it by the treaties and will fight for an improved budget for the EU," said the leader of the Socialist grouping in the chamber, Hannes Swoboda, on Wednesday.
Explaining the demands, a European Parliament official told BBC News that the EU was obliged to pay 217bn euros (£191bn; $283bn) because of contracts already agreed under the current multi-year budget.
The EU treaty says the 27-nation bloc's budget must always balance, so it cannot accumulate debts, unlike national governments.
The official, who asked not to be named, also said the EU still had 16.2bn euros to pay for last year's commitments to projects in Europe's least developed regions.
The parliament argues that such debts must be settled as soon as possible, so as not to jeopardise important long-term research programmes and innovation projects, which are priority areas for the EU in the current economic crisis.
Read more of this report from the BBC.
See also Mediapart's preview of this crucial vote and its implications.