The statement comes on the back of allegations that defeat devices had been found in vehicles, including from environmental activist group Deutsche Umweltilfe (DUH) and magazine ‘Der Spiegel’.

In response Opel pointed to extensive tests conducted in various countries, including Germany and the UK, that have found no evidence of defeat devices being used by anyone except VW.

Opel commented: “We fully cooperated and supplied the Kraftfahrt-Bundesamt (KBA) with extensive data in the fall of last year to support the comprehensive analysis of the German authorities.

“Our software was never designed to cheat or deceive.

“Test methods and protocols of the activities by DUH/Monitor/Spiegel were not shared with Opel which does not allow us to evaluate the outcome. Based on our own and independent measurements and on the experience with experiments published by DUH before, we do not believe that these results are objective or scientifically founded.”

According to reports, Germany’s transport minister has summoned the carmaker to an investigative committee along with Fiat.

Opel also reiterated its support for the introduction of RDE (Real Driving Emissions) testing next year and highlighted its previous announcement that it will publish fuel consumption figures recorded under the WLTP test cycle from June.