The planned emissions-related rise in congestion charge will result in an overall increase in carbon dioxide (CO2) in London, a study shows.

King's College experts predicted a rise in CO2 levels in outer London would outweigh the benefits of CO2 saved by the £25-a-day fee in inner London.

Researchers said this would be largely caused by people driving further to avoid the congestion charging zone.

The report was commissioned by Transport for London (TfL).

It was released after a request from car marker Porsche, which is challenging the price changes in the High Court.

'Unjust' charge
Porsche claims the "unjust" charge will unfairly hit large numbers of drivers in London and undermine London's attractiveness as a place to do business.

Andy Goss, managing director of Porsche Cars GB, said: "We always knew the environmental impact of this unfair tax would be minimal, now we know it will make matters worse."

London's mayor, Ken Livingstone, plans to raise the daily charge from £8 to £25 from 27 October.

Under the plans the cars emitting the highest amounts of CO2 will have to pay a £25 congestion charge whereas cars with the lowest emissions will get a 100% discount.

'High disbenefit'
According to the King's College report, the new charge will create a "very high disbenefit" for CO2 and other components crucial for air quality.

Research revealed there would be an increase in CO2 emitted in Greater London year-on-year from 2009.

It shows that by 2012 the increase in CO2 in outer London would be almost 184,000 tonnes, with just 2,200 tonnes saved in central London, giving an overall increase of 182,000 tonnes.

The study estimated the total impact on CO2 in both central and outer London.

It concluded that because of the new charge, drivers were likely to increase their mileage outside of and around the zone and thus increase their emissions. (bbc.co.uk)