Weekly motoring costs for some households could rise by as much as £20 a week by 2010 if the Government introduced road pricing without cutting fuel taxes.

The £20 increase would be in Greater London, with the average British car-using household seeing weekly motoring bills (excluding petrol costs) rising by £4, a policy report from the Independent Transport Commission (ITC) said.

If road charges were brought but fuel taxes were cut, drivers in urban areas such as London, Birmingham and Glasgow would see more dependable road travel and pollution would decline.

Motorists on busy main roads and motorways would also benefit, although traffic in rural areas would grow, the ITC report said.

The commission also said that charging drivers to use roads at peak times was unlikely to lead to a big switch by motorists to public transport.

Instead, drivers were likely to travel earlier or go in for car-sharing, with few going by bus and even fewer switching to "already crowded trains".

The ITC said the present fuel tax system was "incredibly inefficient" and was bad at doing the job of managing the roads.

It added that a regulator could be set up to decide on the level of any road charges along the lines of the current practice in the electricity and water industries.

ITC chairman Sir Patrick Brown said: "This research shows today's fuel tax to be incredibly inefficient. It does the job of managing the roads badly. Without raising any additional revenue from drivers we could have a more efficient Britain and more comfortable driving.

"The key issues are: Who decides on the level of the charges? And what happens to the money?'." As possible answers, the commission suggests that the roads might become regulated utilities or franchised to independent operators.