The spokesman for German Finance Minister Wolfgang Schaeuble said Tsipras had violated the ground rules of relations among the 19 eurozone countries.
"In terms of comments this weekend in Athens about Spain and Portugal, I can only say that according to European standards that was a very unusual foul," spokesman Martin Jaeger told reporters.
"We don't do that in the Eurogroup. It is not the done thing."
Tsipras had said Saturday that during talks that gave debt-mired Greece a four-month extension to its bailout, pressure from certain other European countries "had the character of blackmail" — pointing especially to Spain and Portugal.
"Conservative forces (in Europe) tried to set a trap for us, to drive us into financial asphyxia," the Greek premier said.
As tensions mounted in the eurozone, Spanish Prime Minister Mariano Rajoy fired back on Sunday calling on Tsipras to "get serious" about his country's economic woes.
Both Madrid and Lisbon, which have closely toed Berlin's pro-austerity line, have filed official protests against Tsipras's comments with Brussels.
Jaeger noted that "Portugal and Spain are partners with whom we work closely together".
"We have a lot of respect for what both countries have achieved in recent years in terms of reforms," he said.
The German parliament on Friday overwhelmingly approved the extension for Greece, based on a compromise reached between Athens and eurozone finance ministers stipulating that Greece will implement reforms and savings.