Volvo is calling on London Mayor, Boris Johnson to uphold a promise to publish a review of what the carmaker labels ‘unfair’ congestion charge exemptions.

After a campaign lead by the Swedish carmaker, the Mayor agreed to review the exemptions with a view to amending a discrepancy in the way alternative fuel and conventionally fuelled cars are charged to drive through the capital.

Currently hybrid vehicles can travel within the London Congestion Charge zone free-of-charge while the driver of a similar, or even lower, CO2 emitting conventional internal combustion-powered car is charged £8.00. This ‘tax’ could add a financial burden of over £2,000 per year to those drivers who have selected a traditionally-powered low emission car.

Volvo, with its lowest emitting model the C30 DRIVe which has start/stop technology emits just 99g/km of CO2 and achieves 74.3 mpg on a combined cycle. Compare this to a hybrid model, like the Honda Insight, which in its cleanest variant still emits a slightly higher level of CO2 at 101g/km and runs to a slightly less efficient 64.2mpg combined.

Volvo has today written to the Mayor asking him to publish the findings of the review of the exemptions as he promised to deliver before the end of 2009.