MOTORISTS face congestion charges on some of Britain’s busiest motorways under government plans to reduce queues by charging by the mile at peak times.

Douglas Alexander, the Transport Secretary, has asked the Highways Agency to identify a suitable section of the 4,800-mile strategic road network for a congestion-charging trial, The Times has learnt.

The M25, London’s orbital motorway, is likely to be considered as it has the worst congestion and traffic is continuing to grow rapidly. A fourth lane is being added to the remaining three-lane sections and one option would be to charge for access to the new lane at peak times.

The trial would be a forerunner to a national charging scheme covering all roads, which the Government has said could be introduced around 2015. Congestion on motorways and A-roads would reduce by 34 per cent if charges of up to £1.34 a mile were introduced, according to a study published by the Department for Transport in 2004.

The Government yesterday demonstrated its determination to use charging to tackle congestion by announcing a 50 per cent increase in the toll for using the M25 Dartford river crossing. From early 2008, the price for cars will rise from £1 to £1.50.

The toll will be scrapped between 10pm and 6am to encourage lorries to travel at night rather than contributing to congestion during the day. Drivers who install an electronic tag and set up a prepaid account will pay only £1.

The move comes despite a promise when the crossing was built to abolish the toll when the bridge and tunnels were paid for. That happened in 2003. Since then, the Department for Transport has received an estimated £200 million from the toll.

The department wants hundreds of thousands of drivers to get used to the idea of having tags in their cars because similar technology could be used for national road charging.

Ministers are planning congestion-charging trials in one or two regional cities, starting in 2010. Cities that agree to take part will be rewarded with up to £200 million extra a year to invest in transport, including better buses and new tram lines. Manchester, Birmingham and Cambridge are the leading contenders to participate in the trials.

A department source said: “We need to test road pricing on motorways as well as in urban areas. If we are serious about addressing congestion, we cannot ignore motorways where many of the worst problems are found.”

Since last month, vehicles have been able to use the hard shoulder on an 11-mile stretch of the M42 at peak times.

Mr Alexander is preparing a road transport Bill that would give the department new powers to introduce charging on motorways. He wrote to Jack Straw, the Leader of the Commons, in July: “We are considering pilots on the trunk-road network as an important stage towards national road pricing.”

The department forecasts that traffic on all roads in England will rise by at least 29 per cent by 2015 and possibly as much as 38 per cent. Traffic on motorways and inter-urban A-roads will grow at a much faster rate, increasing by between 40 and 51 per cent.

The Conservatives said this month that they favoured charging for access to new lanes on motorways and opposed plans to turn some of them into car-sharing lanes.

The AA Motoring Trust said that it would support a motorway charging scheme as long as charges were imposed on new capacity only, such as the extra lanes being added to the M25, M1 and M6. It said that the Government would also have to show that the revenues were being reinvested to improve transport in the trial area.

David Begg, the Government’s former transport ad- viser, said: “All the research shows that motorists are much more likely to accept charging when it is for new capacity rather than existing roads.”

A department spokesman said: “The Highways Agency is involved in work to look at road pricing on a local basis. We need local pilots to give us experience of scalable technology.”