The issue lies with a refrigerant called HFC-134a, used in many cars, but which has a global warming potential (gwp) of 1,320 times higher than CO2.

From 1 January 2013, a new directive from the EU will require all carmakers to limit the gwp of the air conditioning refrigerants they use to less than 150 times higher than CO2.

In response, all European carmakers have thrown their weight behind a refrigerant called HFO-1234yf, which has a gwp of just 4.

However, Daimler has now changed its mind after announcing the simulations have shown that the refrigerant could be highly flammable under certain conditions.

In a statement, Daimler said: ‘Due to the new findings of this study and the high safety demands at Mercedes-Benz, this chemical will not be used in its products. ‘The company therefore wishes to continue to use the proven and safe R134a refrigerant in its vehicles.’

Publication Euractiv has reported that Carlo Corazza, a spokesperson for the EU’s Industry Commissioner Antonio Tajani, said: ‘We expect as a general principle that EU legislation should be respected.’