BMW and Daimler have now suspended senior staff in light of allegations surrounding the testing of diesel emissions on monkeys in the US.

The two German brands had sought to distance themselves from the revelations related to experiments carried out by EUGT (European Research Association for the Environment and Health in the Transport Sector) in 2014 as Volkswagen issued an apology and vowed to investigate the matter

But following Volkswagen’s suspension of chief lobbyist Dr Thomas Steg over the matter, Udo Hartmann, head of environmental protection at Daimler, and Frank Hansen, BMW’s head of urban mobility, were both suspended pending internal investigations The Telegraph reported.

BMW has so far denied any involvement in the study and Daimler has publicly distanced itself, the newspaper said.

It added that, following Wednesday's move to suspend staff at BMW and Daimler, EUGT’s chief scientific advisor had alleged that their representatives had been fully aware of the study.

Prof Helmut Greim told the publication “of course the car manufacturers knew about the tests on monkeys,” adding “The current attitude of the carmakers’ boards doesn’t make sense to me.”

Addressing the media earlier this week a Daimler spokesman told the AFP news agency that it "condemns the experiments in the strongest terms", adding in a statement: "Even though Daimler did not have influence on the study’s design, we have launched a comprehensive investigation into the matter.”

A statement issued by BMW said that it "did not participate in the mentioned studies".