Car maker Daimler described as "questionable" results of emissions tests from one of its Mercedes diesel models cited by German environmental lobby group DUH on Wednesday.
DUH said nitrogen oxide emissions of Mercedes C-Class 200 CDI model had been found to exceed Euro-5 limits, citing tests carried out by the University of Applied Sciences in Bern, Switzerland.
However, a Daimler spokesman said: "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."
DUH said the vehicle released emissions of nitrogen oxides (NOx) that were more than twice the legal limits when tested under new European testing cycles.