David Cameron has called for a dramatic reduction in the pollution emitted by the cars on Britain's roads.

The Conservative leader backed new rules that would require progressively tougher rules on emissions over the next 15 years.

At present the average emission of carbon dioxide from new cars sold in the UK is around 170 grammes per kilometre travelled.

The Tory chief wants this to reduce to a level of 100 g/km in 2022.

And by 2030 he will call for that figure to be an average for all cars on Britain's roads, not just newer models.

He also wants to give manufacturers an incentive to bring new models and new technologies to the market in the UK.

Transport accounts for around 27 per cent of UK carbon emissions - a 47 per cent increase since 1980.

Cameron said he was "setting out how people can vote blue and go green".

"Tackling climate change requires action on every front," he added.

"We must give people, particularly those living in our towns and cities, serious travel options that don’t involve the car.

"Around a quarter of all car trips made are under two miles in length.

"If we're serious about tackling climate change - and, incidentally about improving public health too - we need to help make it possible for people to walk or cycle on these shorter journeys."