Currently, the Alternative Fuel Discount allows alternatively fuelled vehicles, including LPG, natural gas and petrol-electric hybrids, to travel into the capital for free.

However, Transport for London (TfL) has admitted that some new vehicles that do not qualify for this discount have better environmental performance than those that do qualify.

The anomaly, which had been highlighted by Volvo’s Emissions Equality campaign, will now be scrapped from December 24, 2010, with vehicles registered before that continuing to receive a 100% discount for a two-year period.

“I think the changes are going to have the desired effect and force everybody to go greener,” said Danny Alborough, fleet manager at Gratte Brothers. “We will certainly be looking at the vehicles we operate.

“But being a construction company operating in London, the price increase isn’t welcome and we will have to see how we can work to mitigate it.”   

Another review will be conducted in 2012, when officials will decide whether or not to reduce the 100% discount threshold to 80g/km.

TfL has also announced that Fleet Auto Pay will include two important changes: the minimum number of vehicles an operator can register to qualify for an account reduces from 10 to six; and the price increases from £8 to £9 per day.

The Mayor of London, Boris Johnson, said: “It is essential that the Congestion Charge is made fairer and more effective, but also that it continues to do what it says on the tin and remains a deterrent to all but essential journeys into the heart of the capital.”