Some €26 billion in unpaid bills have piled up during 2014, the European Commission tells member states.
The member states demand a cut of €2 billion to the Commission's proposal for the 2015 budget.
Oresharski leaves successor with a difficult set of issues.
Move by member states sets the stage for a budget fight with MEPs.
Eurozone member states agree that the EU must focus on boosting growth and employment, but a push by centre-left governments to relax eurozone budget rules is dividing EU leaders.