While using high levels of carbon dioxide emissions to penalise petrol users, he has simultaneously used particulates and nitrogen oxide emissions as an argument for penalising diesel. As a result he has failed to give fleet managers and company car drivers a clear sense of direction over which fuel is more environmentally-friendly leaving the impression that the duty increases are a pure tax-raising measure.

The controversy will intensify as the Government pursues its goal of introducing a system of graduated vehicle excise duty to incentivise the use of 'cleaner and smaller' cars.