Vehicle manufacturers face an uphill struggle in order to hit tough EU targets on cutting the carbon emissions of their fleets, Clean Green Cars has said.

Under EU legislation, carmakers must slash their greenhouse gas output to 130 g/kg by the end of 2012, yet currently only two firms - Toyota and Fiat - have achieved this goal.

Jay Nagley, publisher of Clean Green Cars, gave a further warning about the figures, explaining that the car scrappage scheme - which finishes in February - was a major contributing factor towards lower emissions.

"The scrappage incentive encouraged buyers to move to smaller cars," he said. "We calculate that half the 2009 improvement [in reductions] was due to the scrappage scheme alone."

Manufacturers will therefore need to improve the performance of their cars "markedly" in 2010, he added.

Despite this, Dr Ben Lane of WhatGreenCar claimed last week that firms are now "fully engaged" with the challenge of designing and selling more eco-friendly motors.