BRUSSELS — The European Commission president, José Manuel Barroso, on Tuesday accused the German government of lacking leadership during the euro crisis and describing its plans to rewrite the European Union’s rulebook as “naïve.”

In an uncharacteristically blunt intervention, Mr. Barroso took issue with German proposals to change the European Union’s Lisbon Treaty so that punishments can be increased for countries, like Greece, that break the rules governing euro countries.

He also suggested that the alarm in the markets, which has destabilized the euro, might have been calmed by quicker assurances of German support.

The comments, made in an interview in the Frankfurter Allgemeine Zeitung, irritated German officials, where some of Mr. Barroso’s claims were dismissed as “absurd” on Tuesday.