Demand for diesel cars continues to rise, and more than 30 per cent of all new cars sold today are oil burners, according to the SMMT.

A year ago, only 26 per cent of new cars were powered by Dr Diesel’s invention, but that figure rose for the 44th successive month in May to 30.9 per cent.

Convertible models have also enjoyed strong demand, with sales up by 32.1 per cent or 12,203 units to 50,203 models over the year-to-date.

The Ford Focus was once again the UK’s best seller in May, while Renault’s M├ęgane climbed to third, with the Vauxhall Zafira in the top 10 for the first time since June 2003.