TfL told What Van?: “TfL considers it unlikely that a congestion charging discount would be a significant additional incentive in this very competitive market where manufacturers already strive to produce fuel efficient vehicles.”

But despite highlighting the best efforts of manufacturers to cut emissions, TfL pointed out that, apart from electric vehicles, which already qualify for a 100% discount, only the Ford Fiesta Van had emissions below the 100g/km threshold for exemption from the fee. It claimed this van would “not meet the business needs of many operations” and therefore would not prove popular with fleets even if not liable the charge.

Under changes to the scheme that will come into force on 4 January 2011, passenger cars that emit up to 100g/km CO2 and meet the Euro 5 standard for air quality will qualify for the Greener Vehicle Discount and not be liable to pay the charge, which will increase from £8 to £10 per day.

TfL admitted that because the DVLA does not record the CO2 limit of vans and HGVs, it would be difficult to administrate the GVD for commercial vehicles.

It added: “It is considered that a discount for commercial vehicles is unlikely to incentivise the uptake of the cleanest vehicles as it is a small amount of the running cost.” The Government body said running costs for vans must also include the driver’s wages.

Vans are included in the 100% discount for fully electric vehicles, which TfL is to extend to cover plug-in hybrid electric vehicles from next year. LPG vans will also continue to qualify for the Alternative Fuel Discount until it is withdrawn in December 2012.