The proposal by the European Commission to cut carbon dioxide emissions from cars by a fifth by 2012 will hit luxury vehicles made by the German firms Porsche and Mercedes-Benz and the Japanese companies Mazda and Subaru hardest, commission officials have confirmed.

The final version of the plan published just before Christmas calls for a cut in average emissions to 120g/km by 2012 with fines for every gram a company’s average exceeds the limit across the range.

It is expected that the German government will make strenuous efforts to water down the proposal.

The commission said that Porsche’s range had an average CO2 emission profile of 282g/km in 2006 followed by Subaru at 216g/km, DaimlerChrysler (184g/km), BMW (182g/km) and Mazda (173g/km).