The two German car makers have have been forced to respond to the monkey emissions test controversy.

Mercedes and BMW have moved in response to the recent monkey emissions test controversy by suspending or moving employees.

Both companies, along with Volkswagen, have been publicly blasted after it was revealed that the trio funded an experiment in the United States that forced monkeys to inhale diesel fumes in a bid to prove the safety of the fuel following a decision by the World Health Organisation to declare that the fumes were carcinogenic.

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Volkswagen has already suspended its chief lobbyist, Thomas Steg, a former German government spokesman who was in charge of maintaining the company's relationship with the European Research Group on Environmental and Health in the Transport Sector (EUGT) and helped design the study.

Daimler has since suspended an employee linked with the controversy and has hired a law firm to investigate the matter. Meanwhile, BMW has also removed an employee from his position pending an investigation into the study by its own legal panel. Neither company has revealed the names of those involved.

'The board of management of Daimler AG has decided to suspend the employee, who was a member of the board of EUGT,' Daimler said in a statement, while reiterating that they had no say in how the test was carried out. In another statement released earlier this week, Daimler withdrew its earlier support for the tests, saying: 'We distance ourselves from the LRRI study done under EUGT. Daimler does not tolerate or support unethical treatment of animals'.

Volkswagen chief executive Matthias Müller also called out the tests earlier this week. 'The methods used by EUGT in the United States were wrong, they were unethical and repulsive,' he said on Monday. 'I am sorry that Volkswagen was involved in the matter as one of the sponsors of EUGT.'

The tests are said to have taken place as far back as 2014, and the EUGT was disbanded last year.