Fiat tops the volume-weighted European average league for CO2 emissions at 137.3g/km and the top six manufacturers are now below 150g/km, according to UK analysts Jato Dynamics.

Research of the volume-weighted average CO2 emissions in 2007 for the 10 best selling car brands in Europe showed that Fiat was ahead of Peugeot, which achieved an average CO2 rating of 141.9g/km last year.

Citroen (142.2g/km), Renault (146.4g/km), Toyota (148.8g/km), completed the top five places in the European league while Ford (149.1g/km), Opel/Vauxhall (152.9g/km), Volkswagen (161.7g/km), BMW (176.7g/km) and Mercedes (188.4g/km), rounded off the top 10.

"The entire industry has made incredible advances in reducing CO2 emissions", said Jato spokesman Nasir Shah. "The Fiat group is currently spearheading the revolution, but it's fair to say that all manufacturers have made remarkable progress in recent years.

"Clearly, when analysing volume-weighted average CO2 figures, it's the manufacturers with product portfolios dominated by small cars that will perform the best. Given the product range of both BMW and Mercedes, their respective performances are particularly impressive."