Mayor Ken Livingstone has announced that, from October, the highest polluting vehicles will have to pay £25 to enter London’s congestion charge zone. But, in addition, some of the cleanest cars will receive a 100 per cent waiver of the congestion charge.

Owners of cars emitting more than 226g/km of carbon dioxide will have to pay the £25 charge – up from the current £8 per day. Cars which fall under this bracket include the Range Rover, BMW 730i and Porsche Cayenne.

However cars which emit less than 120g/km will be exempt from the charge. Cars which will become exempt from the congestion charge include the entry-level Fiat 500, Volkswagen Polo BlueMotion, Seat Leon Ecomotive and Mini Cooper Diesel.

And hybrid cars such as the Toyota Prius and the Lexus RX400h 4×4, which emits 190g/km, are excluded thanks to their technology. However, this exclusion will only apply until January 2010, and hybrid cars bought after this date will not not be entitled to the discount.

Mr Livingstone said:

Nobody needs to damage the environment by driving a gas-guzzling Chelsea tractor in central London. The CO2 emissions from the most high-powered 4×4s and sports cars can be up to four times as great as the least polluting cars.

The CO2 charge will encourage people to switch to cleaner vehicles or public transport and ensure those who choose to carry on driving the most polluting vehicles help pay for the environmental damage they cause.

This is the ‘polluter pays’ principle. At the same time, the 100 per cent discount for the lowest CO2 emitting vehicles will give drivers an incentive to use the least polluting cars available.

The London congestion charge was introduced in February 2003, and required motorists to pay £5 to drive into certain parts of London. In July 2005, Transport for London increased the charge to £8 and, last year, the zone was extended to include most parts of Westminster, Kensington and Chelsea.