New cars got greener in UK last year thanks to the government's "cash for bangers" vehicle scrappage scheme, it was announced yesterday.

On average, new cars emitted 149.5g of CO2 per one kilometre in 2009 - a 5.4 per cent reduction on the average 2008 figure, according to a report from the Society of Motor Manufacturers and Traders.

This was the best year-on-year improvement since the SMMT began to keep records of this kind in 1997.

SMMT chief executive officer Paul Everitt said the scrappage scheme was a key contributor to the lower emission figure last year. The average emissions of cars bought through the scheme were 133.3g per kilometre, which was 26.8 per cent below the 182.3g/km average of the vehicle being scrapped.

Mr Everitt added: "Since figures were first recorded in 1997, average new car CO2 emissions have fallen from nearly 190g/km to less than 150g/km - a 21.2 per cent improvement.

"The industry is well on its way to meeting EU regulatory targets of a 130g/km fleet average by 2015, but the current rate of improvement must be maintained."

He went on: "While economic factors may have contributed to 2009's success, in the longer term slower fleet renewal and a reduced willingness to invest in new technology may undermine this progress."