The announcement is also expected to signal the end for Britain's high-speed Intercity 125 trains, which are set to be replaced after 30 years of service.

The plans are to be unveiled by Transport Secretary Alistair Darling at a rail industry conference in London.

They are intended to help the railways cope with record passenger numbers.

Trains are now taking the greatest number of passengers since the 1950s.

One billion journeys were made by rail last year, prompting the need for bigger trains and better tracks.

To do this the government will propose replacing the Intercity 125 with a new train over the next decade, BBC transport correspondent Tom Symonds said.

He said the government was also considering introducing a new high speed line between London and Scotland.

Mr Darling is expected to announce further plans for high speed services between London and all major towns in England.

Radical restructuring

While the government has been eager to point out that the railways are expanding, there are fears that services are being cut and that capacity has reached its full limit.

Shadow transport secretary Chris Grayling, also speaking at the London conference, will say that Network Rail is not providing for the increasing passenger population and should undergo radical restructuring.

He is also expected to say rail improvements are not being carried out as planned, despite a five-fold rise in public subsidy for them.

Environmental transport group Transport 2000 said the government must not miss the opportunity to create a positive future for railways.

"The government must prevent the railways from falling into further decline and contraction and open them up to meet rising demand on what is, after all, Europe's fastest-growing network," the group said.

A rail White Paper is due to be published next year.