Figures from the Society of Motor Manufacturers and Traders have revealed that new cars are now 18% more fuel-efficient than the average car on the road, while CO2 emissions for the average new car fell by 4.2% in 2011.

Revealed in the organisation’s 11th annual New Car CO2 Report, the data showed that the average emissions level for a new car dropped to 138.1g/km last year – which equates to 52.5mpg – marking a reduction of 23% since the SMMT’s first report in 2000.

Cars emitting less than 100g/km of CO2 had almost doubled their market share to 3.4%, while executive and sports cars marked the biggest reductions in CO2 by sector with drops of 9.5% and 7.0% respectively.

Diesel-engined cars continued to dominate the market with a 50.6% share, while alternative-fuel models now account for 1.3% of the total.

Paul Everitt, SMMT chief executive, said: “The industry can be proud of the progress it has made in reducing CO2 emissions and improving fuel efficiency. We are seeing steady improvement in conventional technologies and the emergence of a range of alternative technologies, creating one of the most innovative periods for the global automotive industry.”