German Finance Minister Wolfgang Schaeuble accused Greece's ruling Syriza party of misleading voters at the last election by promising they could stay in the euro without having to face major reforms.
The pointed words, in an interview published on Wednesday, will do little to soothe tensions building up between Athens and its international creditors as they try to agree on a deal to unlock remaining bailout funds.
"Europe is based on mutual trust. You have to act sensibly, that is what makes the current talks with Greece so tiring," Schaeuble told Wirtschaftswoche weekly.
"In the last election, Syriza succeeded in talking Greeks into believing there is a simpler way to stay in the euro - a way without major reform efforts that are actually in Greece's interests," said Schaeuble.
"Perhaps they shouldn't have made promises like that," he said, adding he had repeatedly tried to find a way to let Greece stand on its own feet.
Greek Prime Minister Alexis Tsipras heads to Brussels on Wednesday to meet European Commission President Jean-Claude Juncker in efforts to clinch a deal before the country runs out of cash.
European Parliament President Martin Schulz said there was no power struggle between Berlin and Athens over reforms but that Greece had a duty towards other European countries that had given it a lot of support.
"Therefore Athens must push ahead with reforms," he told Bild daily.
Greece's government can make no more concessions in negotiations for a cash-for-reforms deal and its international lenders must take responsibility for their role in the talks, Labour Minister Panos Skourletis has said.