Lorry drivers will converge on London today in protest at soaring fuel prices as pressure builds on Prime Minister Gordon Brown over plans for a steep hike in road tax Hundreds of hauliers are expected to protest in the capital over increasing prices which have resulted in the average cost of diesel passing far beyond the 120p-a-litre mark.

It comes as the Government faces another potentially damaging rebellion over tax after backbenchers urged Chancellor Alistair Darling to rethink plans announced in the Budget for big increases in vehicle excise duty on "gas guzzling" cars.

Although vehicles bought before 2001 are exempt, MPs are concerned that the some owners who bought bigger cars in the past not realising the changes were on the way, could be faced with increases of up to £200.

More than 30 Labour backbenchers have signed a Commons motion urging ministers to rethink the vehicle excise duty proposals.

The demands are another headache for Mr Darling and Mr Brown at a time when the Prime Minister is already weakened by the debacle over the 10p tax rate and Labour's disastrous performance in the council elections and the Crewe and Nantwich by-election.