“Bush wants to distract attention from his own internal difficulties. That’s a favourite method. Hitler also did it,” Herta Däubler-Gmelin, was quoted by the Schwäbische Tagblatt newspaper as telling trade unionists in Tübingen.

She said that Mr Bush’s main motivation for such a tough stance against Iraq was not concern for oil supplies, but because the economic crisis had caused his popularity ratings to fall: “The Americans have enough oil themselves.”

The paper also quoted her as saying that the US had a “lousy justice system” and that if today’s laws against insider trading had applied in the Eighties, “then Bush would be sitting in prison today”.

Opposition conservatives vying to defeat Chancellor Schröder’s Social Democrats in Sunday’s election called for her resignation.

Ari Fleischer, President Bush’s spokesman, sought to play down the impact on the relationship between the countries, but reacted strongly to the minister’s remarks.

“The United States and Germany have a very long and valuable relationship, and relations between the people of the United States and Germany are very important to Americans,” Mr Fleischer said. “But this statement by the Justice Minister is outrageous and inexplicable.”

The minister later released a statement to try to limit the damage and won Herr Schröder’s backing.