Chancellor Angela Merkel's deputy spokesman, Thomas Steg, said there was no cause to criticize Schroeder. He said he assumed that Schroeder's remarks to Iranian leaders were in accord with German policy towards Iran.
Schroeder's office has described the trip as a private one at the invitation of a friend, Majid Samii, who is an eminent Iranian-born neurosurgeon. Iran's Foreign Ministry also insisted it was not a political trip.
Schroeder had abided by the rules governing former German chancellors, and had informed Merkel's office well in advance, Steg said.
Steg did not say whether or not Schroeder would be briefing Merkel officials after his return.
A member of Schroeder's Social Democratic Party (SPD), federal deputy Rolf Muetzenich, said in an interview that Schroeder had made the trip at "precisely the right time," after peace feelers to Iran from US President Barack Obama.
"We have to discover whether Iran is willing to embark on a new approach too," said Muetzenich. "You can only discover that on the spot."
During the four-day trip, Schroeder spoke to the Iranian Chamber of Industry and Commerce in Teheran, criticizing the Iranian president's stance against Israel and denial of Holocaust history.