Greece has rejected a German proposal to appoint a European Union commissioner with the power to veto Greek budgets.
A government spokesperson says only Greece should have control over tax and spending.
Greek government spokesman Pantelis Kapsis said Greece's budget must absolutely remain its own responsibility.
The spokesman for the centre-left Pasok party, one of the parties in Greece's coalition government, said a similar idea had been raised before and should be avoided.
The European Commission says it wants to reinforce its monitoring of Greek finances, but Greece should retain sovereign control.
German officials suggested the commissioner would ensure Greek government revenue was spent on paying off the country's huge debts.
Meanwhile, Greece and its private investors are close to a deal with will pave the way for a second bailout.
Negotiators say a tentative agreement could be finalised next week.
But a BBC correspondent reports that because Greece has repeatedly failed to meet earlier fiscal targets, and has made little progress on public-sector reforms, there is concern that even with a deal on the next bailout, Athens may need more than the 130bn euros agreed last October.