German environmental lobby group DUH turned on carmaker Daimler yesterday, saying test results had shown nitrogen oxide emissions from one of its Mercedes diesel models far exceeded European legal limits.

Daimler described the results from the Mercedes C-Class 200 CDI model as “questionable”.

Citing tests carried out by the University of Applied Sciences in Bern, Switzerland, DUH told a news conference that the model had released emissions of nitrogen oxides (NOx) that were more than twice the legal limits when tested under new European testing cycles.

The carmaker took issue with DUH’s assertions.

“The test results are questionable as the conditions of the test are not clear. We don’t know the specific car, the temperature at the time of the tests, the loading weight,” a Daimler spokesman said.

Fellow German carmaker Volkswagen is engulfed in a scandal after rigging the results of exhaust emissions tests in the US.

DUH accused Daimler in September of also rigging emissions data, charges the company denied. The following month it said a model built by General Motors’ Opel division had shown excessive emissions of nitrous oxide, a claim that was denied by Opel at the time.

French rival Renault has also contested findings cited by DUH that one of its minivans released toxic diesel emissions 25 times over legal limits.

Separately, public prosecutors in the German city of Stuttgart said yesterday they were investigating whether staff at auto parts supplier Robert Bosch GmbH were involved in the rigging of emissions tests by Volkswagen.

Stuttgart-based Bosch, which makes a diesel engine management programme used by several top automakers including VW declined to comment on specific investigations.

However, a company spokesman said: “We are cooperating in principle with all authorities whowant to contribute to the clarification of the facts.”