German daily Stuttgarter Zeitung reported at the weekend that a research organization funded by German carmakers sponsored scientific experiments testing nitrogen dioxide, a gas found in exhaust fumes, on people.
Separately, BMW, Daimler and Volkswagen have condemned emissions experiments involving monkeys.
"These tests on monkeys or even people are in no ethical way justifiable and raise many critical questions about those who are behind the tests," government spokesman Steffen Seibert told a regular government news conference in Berlin.
"The supervisory bodies of those who issued these contracts have a special responsibility," he added.
(Reporting by Joseph Nasr and Tom Koerkemeier; Writing by Paul Carrel)
