Transport for London is consulting on reducing the 100% discount level for the London congestion zone from 100g/km to 80g/km.

However, while the review is being carried out this year, TfL told Fleet News no change to the threshold would be carried out this year.

Fleet News revealed in April 2011 how Isabel Dedring, the London Mayor’s environment advisor, has suggested that all new cars with emissions above 80g/km of CO2 could be liable for congestion charge zone fees from 2013.

Currently, fleets have to pay £10 per vehicle per day (£9 if registered for Congestion Charging Auto Pay), but qualify for the Greener Vehicle Dicount (GVD) if a car emits 100g/km or less of CO2 and meets the Euro 5 standard for air quality. A fleet registers the vehicle with Transport for London (TfL) for the discount and pays £10 a year per vehicle.

Orginally, TfL allowed an Alternative Fuel Discount which gave alternatively fuelled vehicles, including LPG natural gas and petrol-electric hybrid vehicles, the right to travel into the capital for free.

However, in October, 2010, it admitted that some new vehicles that did not qualify for this discount had better environmental performance than those that did.

The anomaly, which had been highlighted by Volvo’s Emissions Equality campaign, was scrapped from December 24, 2010, and the existing rules were introduced.

However, an 80g/km limit from 2013 would result in a large number of sub-100g/km vehicles, currently popular with fleets, falling foul of the new rules.

A TfL spokesman said: “The Greener Vehicle Discount provides a 100 per cent discount to cars that emit 100g/km of CO2 or less and meet the Euro 5 standard for air quality.

“TfL will monitor developments in the market and keep discount criteria under review, with the intention of reducing the discount levels to 80g/km or lower when the time is right. The review of exemption criteria will be carried out in 2012.”