Figures by the SMMT demonstrate that the average new car is now 18 percent more efficient than the average car on the road, showing just how far car companies have come in the battle to lower emissions.

Since the year 2000, new car emissions (as in, the average CO2 emissions of all the cars sold) have fallen by 23%; in 2011, emissions dropped by a significant 4.2% compared to 2010.

With new car buyers generally ruminating on their choices with greater emphasis on CO2 emissions and fuel economy (be it for environmental or financial reasons), the eco gulf between new cars and old is widening.

In 2011, over half the new cars bought on the UK had emissions below 130g/km, and over 65,000 were exempt from Vehicle Excise Duty on account of having sub 100g/km emissions.

The executive car segment has seen the biggest drop in emissions over the last decade, falling by a massive 35%

SMMT chief executive Paul Everitt said: "Industry can be proud of the progress it has made in reducing CO2 missions 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."