|PIC1|Hundreds of lorry drivers were converging on London and Cardiff on Tuesday in protest at soaring fuel prices.

The convoys through Kent and along the M4 come at the same time as Chancellor Alistair Darling faces opposition from Labour MPs about a planned increase in road tax on older, more polluting vehicles, which could affect millions of motorists.

The hauliers complain that their key cost has jumped by almost 50 percent since early last year.

Diesel prices have topped 120p a litre, and there is a planned 2p fuel tax rise.

Without government action, some firms will go out of business, the Road Haulage Association warned.

It is calling for a fuel duty regulator to stabilise prices, and is to hand in a petition to 10 Downing Street.

In a letter to Angela Eagle, parliamentary secretary to the Treasury, the association's chief executive Roger King said rising fuel costs will contribute to inflation and hold back investment in the sector.

"It is now almost seven years since Gordon Brown said that the fuel duty level in the UK was unfair compared with our foreign competitors and said he would level the playing field with the lorry road-user charge. Nothing has been achieved," he said.

The government is also coming under pressure from Labour MPs and the media about its plan next year to increase road tax for vehicles registered since 2001 which emit higher levels of pollutants.

Under Budget proposals, owners of the most polluting cars could face a tax rise of as much as 200 pounds a year.

Labour MPs are concerned the retrospective hike could alienate so-called Mondeo Man, the name given to middle-income voters it has tried to woo.

John Hutton, Business Secretary, said the chancellor was listening to people's concerns.

"We have got to listen to what people have to say," he told BBC radio. "But with 24 out of the 30 most popular models, drivers will generally pay less vehicle excise duty than they do now.

"So we are trying to get this balance right between encouraging choices to go green but not hammering it."