London mayor Boris Johnson should concentrate on electrifying the city's taxis and buses, rather than rolling out charging points for privately-owned cars.

This is the view of Stephen Knight - a Liberal Democrat London Assembly environment spokesperson - who thinks a previous campaign to introduce 800 charging terminals across the city for electric vehicle owners to use has failed to generate enough interest.

He suggested that three-quarters of these power points were not used at all in 2012 and it would make more sense for Mr Johnson to focus on replacing the 20,000 diesel taxis and 8,500 buses with more eco-friendly models.

"It is these diesel vehicles which clock up the most miles and make the greatest contribution to air pollution, especially in central London," Mr Knight commented.

The mayor is clearly committed to providing better, greener public transport - a point that is backed up by his support for the eco-friendly New Bus for London rollout.

It is hoped that by 2016, 20 per cent of the capital's buses will be hybrid vehicles.