It has emerged that just 52 of the 1,300 extra carriages announced last week by Transport Secretary Ruth Kelly will go to embattled train operator First Great Western, which runs services to Bristol and London.

Most of the new rolling stock, 900 carriages, will go to London and the South East, while more than 300 will be used to meet the growth in demand in cities such as Birmingham, Leeds and Manchester.

Ms Kelly said the extra carriages would increase the amount of rolling stock by 10 per cent, which would enable Network Rail to plan changes such as longer platforms at stations.

She told MPs: "In some areas the extra capacity will be secured through the procurement of new rolling stock, and in other areas it will be secured through redeploying existing rolling stock which is displaced by new.

"The redeployment of existing carriages will mean longer trains can run on busy routes and at peak times."

She said FGW would also introduce additional rolling stock for services around Bristol.

But it will bring little comfort in the short term to hard-pressed FGW customers who already endure severe overcrowding, significant fare increases, poor levels of punctuality, and cuts in services.

MP for Bath Don Foster said: "The real problem is this is a medium- to long-term plan. It doesn't help solve our immediate problem.

"We already have significant overcrowding on our trains. We desperately need an interim solution."

He blamed the crisis on the Government, having agreed a franchise providing less rolling stock.

Mr Foster said: "Some was taken away from us. That was clearly a huge mistake for which we are paying the price."

He added: "I have been advised that today we are short of 36 carriages of delivering even an adequate quantity for the current number of passengers.

"With growth increasing rapidly, more will be needed in the future."

Meanwhile, Westbury MP Andrew Murrison - whose constituency covers Bradford on Avon, has asked for a meeting with Rail Minister Tom Harris over the state of local services.

He said he was "appalled" by the deterioration in FGW's service, and that it was time to take the franchise away from the firm.

"FGW has been given plenty of time to improve but my constituents are still suffering from a third-rate train service.

"I think the time has come for ministers who are responsible for the contract to consider pulling the plug."

He will meet FGW chief executive Andrew Haines at a meeting of the West Wilts Rail Users' Group in Trowbridge next Thursday, and again in London on Tuesday, February 19.

Pressure group Railfuture Severnside says the extra rolling stock announcement is "a step in the right direction" but not enough to keep up with demand.

FGW, whose performance sparked a protest on the trains last week, welcomed the announcement. A spokesman said that capacity issues and the need for extra carriages on part of its service were "well-documented".

A Department for Transport spokesman said: "Over £10 billion is being spent on tackling overcrowding. Benefits will be felt by passengers."