The New York Times on Friday said German carmakers had used the European Research Group on Environment and Health in the Transport Sector, also known as EUGT, to commission a study created to defend the use of diesel following revelations that the fuel's exhaust fumes were carcinogenic.
'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.
Daimler AG said it was "appalled by the nature and extent of the studies" and said that, though it did not have any influence on the studies' design, "we have launched a comprehensive investigation into the matter".More news: Bruno Mars cleans up at Grammy Awards
"We believe that the scientific methods used to conduct the study were wrong and that it would have been better not to undertake it at all", Volkswagen said in a statement on Monday.
"The fact that an entire industry has apparently tried to hide brazen and dubious methods of scientific research makes it even more monstrous", she said.
Daimler - parent company of Mercedes - said the animal experiments were "repulsive".
Following global outcry over the weekend, all three auto manufacturers involved have issued statements trying to disassociate themselves from the activities of the research institute.
It remains unclear whether the carmakers were aware of monkeys being used in the experiments. However it does admit that the EUGT did carry out animal testing.More news: Bristol-Myers Squibb Co (BMY) Shares Sold by Boston Private Wealth LLC
The goal was to compare the results of the Beetle emission to those of a 1999 Ford diesel pickup and debunk a World Health Organization report that claimed diesel exhaust is a carcinogen.
News of the medical test in Germany has awakened uncomfortable memories of the Third Reich. They were meant to show modern diesel technology had solved the problem of excess emissions.
"The outrage felt by many is absolutely understandable, " he added.
But the clean air study was actually a fraud with one of the cars - a VW Beetle - reportedly fitted with the diesel cheating software meaning it was belching out 40 times over legal limits. In real life, the vehicle produces "40 times the permitted limit", according to the paper.
As of late 2017, dealing with the scandal had cost Volkswagen a total of $30 billion.More news: Sui Dhaaga: Anushka Sharma BEGINS preparations!