London mayor Ken Livingstone has announced that the congestion charge for higher-emissions vehicles is to rise to £25 from 2009.
Despite being called a congestion charge, the new tax will in future take into account a car's emissions. Vehicles in Road Tax band G - those that emit more than 225g/km of CO2 - will be charged the higher rate.
This means, for example, that the driver of a Renault Espace 2.0T (232g/km) would pay £25 to drive into central London, while the driver of an Espace 2.2dCi (211g/km) would pay £8. This is despite both vehicles being the same physical size, and therefore causing the same amount of congestion.
London residents who live within the scheme – who currently qualify for a 90 per cent discount – will no longer get any discount if their car is in Band G.
Meanwhile, in 2008 the charge for the least-polluting vehicles – those in Band A and B, which produce less than 120g/km – will be removed.
"Most vehicles that will be charged £25, in vehicle excise duty band G, are high-priced models," said Livingstone.
"Those who buy them can afford to choose from pretty much the whole of the mainstream car market but have chosen to buy one of the most polluting vehicles."
Livingstone's charge could hit families hard. A 2.0T Espace could be carrying seven people, while the Porsche Boxster, for example, which emits 201g/km, can only carry two.
The wider significance of the change in the London congestion charge is that it reflects forthcoming national policies. Plans for nationwide road tolls are set to get the go-ahead this week and, like the London charge, they will also be vary according to a car's CO2 output.