Latest figures show the average new car sold in 2003 emitted 9.3% less CO2 than models registered in 1997.
Produced by the Society of Motor Manufacturers and Traders (SMMT) and based on data from every new car registered last year, the figures also show a 1.2% year-on-year drop from 174.2 g/km in 2002 to 172.1 g/km in 2003.
The third annual report, 'UK New Car Registrations by CO2 Performance', highlights how the carbon dioxide-based company car tax system has had an impact since its introduction in 2002. It notes a growth in sales of superminis, more diesel models and a growing demand for alternatively-fuelled vehicles.
SMMT chief executive Christopher Macgowan said: 'Fiscal measures have certainly helped focus buyers' attention on carbon dioxide emissions. 'However, as the latest SMMT data shows, market change is a gradual process. The incentives that drive the growth of cleaner vehicles must be transparent if buyers are to be confident in their decisions to buy greener, low carbon vehicles.
'Stability was the theme of the Chancellor's March Budget, with a freeze on many CO2 based motoring taxes. Our common goal of lower CO2 emissions will be realised if that theme continues in the years to come.' Findings in 2003 include: