A report written by Lib Dem MEP Chris Davies, to be debated by Parliament in October, says a fifth of car adverts should consist of a kind of health warning for the earth, highlighting cars' fuel efficiency and CO2 emissions.

It would also be illegal for ads to boast about cars going faster than the national speed limit.

The report takes this speed limit concept a step further and proposes a ban on cars that can do more than 101 mph (25 per cent more than the average upper speed limit) altogether. Only emergency, military and police vehicles would be exempt from the law, which would be introduced in four years' time. Davies noted that the power of new cars increased by 28 per cent between 1994 and 2004, making them heavier and thus increasing the amount of CO2 output. This increase is completely unnecessary, the MEP said, as no country has raised its speed limit to allow cars to use this additional power.