"The death penalty is the ultimate violation of human rights and the right to life," Green party leader Claudia Roth told the Bild newspaper, adding that Obama should work for abolishing the death penalty in the US, not expanding it.
The US Supreme Court handed down a 5-4 decision on Wednesday invalidating a Louisiana law that allows capital punishment for people convicted of raping children under 12. The court said it violates the US Constitution's ban on cruel and unusual punishment.
Obama said afterwards that states should have a right to consider the death penalty for such a crime.
In Germany, the criticism of his statement ran the length of the political spectrum.
The head of the conservative, Bavaria-based Christian Social Union, Erwin Huber, said: "Child rape one of the most heinous crimes, but the ban of the death penalty must be absolute."
The foreign policy spokesperson of the Union bloc of conservatives, Eckart von Klaeden of the Christian Democratic Union, was critical of the outbreak of "Obamania" in Europe. He said many were mistaken if they thought "they could gauge Obama by European standards."
Sabine Leutheusser-Schnarrenberger of the Free Democrats, a former justice minister, made a plea to the candidate: "Mr. Obama, the dealth penalty should be abolished around the world." She said it was just as inhuman as the crime of child rape.