The Mayor of London is reviewing the exemption of alternative fuel vehicles from the congestion charge after Volvo launched a campaign claiming the current system unfairly biases hybrid cars over other low-emitting vehicles.

In response to the campaign, Boris Johnson confirmed that the exemption to the Congestion Charge was introduced to incentivise the take-up of more environmentally-friendly vehicles but recognised that vehicle technology has developed considerably since then.

Transport for London will report their recommendations by the end of the year.

The news comes as a What Car? poll confirmed that the motoring public also believe that the current hybrid and electric car exemption is outdated and unfair.

In the poll, 50 per cent of over 1,500 respondents said they believed any exemption should be CO2 based while only 34 per cent believed that the status quo, where all hybrid or electric cars are exempt, is fair.

Last month, Volvo Europe regional president Stuart Kerr wrote to Johnson, highlighting the disparity between the treatment of hybrid and conventional internal combustion-engined cars.

Drivers of hybrid cars enter the zone free of charge on a daily basis while drivers of low emission cars powered by conventional internal combustion engines with the same, or even lower, levels of emissions are charged £8.00 per day. This could add a financial burden of over £2,000 per year to those drivers who have selected a traditionally-powered low emission car.