The average CO2 emission rating has been creeping up since the end of the scrappage scheme rather than continuing the constant reduction in CO2 emissions that is needed to meet EU targets in 2012.

The scheme officially ended in April, when the average CO2 emission of new cars sold was 144.93g/km, but it has crept back up to 145.26 for the cars sold in June. There were 10,000 cars bought with assistance from the scrappage scheme in April, and just 1,200 in June.

The numbers might not seem huge, but for car manufacturers to be on target to get their average emissions under the 130g/km barrier that the EU has said will be imposed from 2012, the makers need the figures to be going down rather than staying still. Average emissions need to drop by around five percent a year if manufacturers are to hit targets.

Currently there are only three manufacturers that have made it under the 130g/km barrier – Toyota, Fiat and Mini with emissions of 124.49 g/km, 125.05 g/km and 129.33 g/km respectively.

"Car manufacturers are swimming against the tide now that the scrappage scheme has ended," said Jay Nagley, publisher of Clean Green Cars, who conducted the research. "They are going to have to redouble their efforts to meet what is a reasonable overall target."