The Mayor of London has announced that the lowest emission cars - in VED bands A and B - will receive a 100% discount from the £8-a-day London Congestion Charge. Meanwhile, the highest emitters - Band G vehicles - will pay a daily charge of £25 to drive in the Congestion Charge zone. The changes will be introduced on October 27th this year.

The scheme is a major plank of the Mayor's Climate Change Action Plan, which aims to reduce London's CO2 emissions by 60 per cent by 2025.

VED Band A and B are those which emit less than 120g of CO2 per kilometre. Where these vehicles also meet the strict Euro 4 air pollution emission standard they will become exempt from the daily charge. Band G cars (including cars registered pre 2001 with engines over 3,000 cc), to be charged £25 to drive in the zone, are those in which emit over 225g of CO2 per kilometre.

17 per cent of the cars currently driven in the zone are Band G vehicles which would be liable for the £25 charge while just two per cent are from Bands A and B which will qualify for the 100 per cent discount.

Ken Livingstone, said: "The CO2 emissions from the most high powered 4x4s and sports cars can be up to four times as great of those of the least polluting cars. The CO2 charge will encourage people to switch to cleaner vehicles or public transport and ensure that those who choose to carry on driving the most polluting vehicles help pay for the environmental damage they cause."

"We will be closely monitoring this scheme to ensure that goal of reducing traffic congestion in central London remains a central priority.

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Sheila Rainger, acting director for the RAC Foundation, (quoted on the BBC website) said: "The congestion charge was originally developed to reduce congestion. Changing this will confuse the public and reduce support and trust for future initiatives."

Friends of the Earth's Executive Director, Tony Juniper, said: "Road traffic is one of the biggest contributors to climate change. Measures that get people to choose greener cars, as well as to drive less, are urgently needed. Charging gas-guzzling vehicles more to drive in central London is extremely welcome and supported by most Londoners. We are delighted that Mr Livingstone is taking a lead on this issue.”

Boris Johnson, the Conservative candidate for London Mayor (also quoted on the BBC website), said: "In effect, the mayor has just given the green light for richer people to buy smaller cars and enter the zone for free while families who struggle with one big car are left feeling the pinch."