File picture: Kacper Pempel / Reuters.

Berlin - Volkswagen tried to hide the results of a diesel emissions test on monkeys because it showed a worse health impact than expected, a German news report claimed on Wednesday.

The Bild daily reported that the exhaust fumes tests on 10 monkeys that have sparked fresh public outrage following VW's emissions-cheating scandal "were never supposed to come to light" because the results were "too devastating".

Amid a storm of criticism over the experiment and over separate tests on German human volunteers commissioned by an auto industry-financed research institute, VW on Tuesday suspended its chief lobbyist Thomas Steg and labelled the testing "unethical and repulsive".

The US study using monkeys in an Albuquerque laboratory, which VW said took place in 2015, was meant to show that the diesel exhaust fumes from a VW Beetle were cleaner than those from an older Ford pickup.

"This was not what the results showed at all, however," reported Bild, citing internal study papers, despite the fact that the VW model had been fitted with a so-called defeat device that reduced emissions while testing.

The Bild report said that after four hours of exposure, blood was taken from the animals and a special endoscope was inserted into their windpipes and bronchia through their noses or mouths.

It said some of the monkeys that had inhaled VW fumes showed a higher degree of inflammation than other animals.

The human and animal tests were commissioned by an organisation funded by VW, Daimler and BMW, the European Research Group on Environment and Health in the Transport Sector, which has since been disbanded.

Agence France-Presse