The lengthy closure of parts of the West Coast main line for track upgrades will have minimal impact on intercity passengers, Railtrack has insisted.

Local commuters could face severe disruption, however, with some journey times doubled in areas affected by the work, which will start next summer.

But rail passenger groups believe a "short sharp" interruption to services caused by the multi-billion-pound upgrade will bring overall long-term benefits.

And Transport Secretary Alistair Darling said a major overhaul of the country's busiest line was long overdue and the temporary inconvenience was necessary if the railways were to improve.

The West Coast Main Line will be closed for 40 miles near Stoke-on-Trent while an upgrade is carried out.

The programme would see the line shut for 17 weeks from Colwich in Staffordshire to Cheadle Hulme, just south of Stockport, next summer.

This will be followed by a second 17-week closure early in 2004, from Crewe to Cheadle Hulme.

A Railtrack spokesman said the difference in journey times for intercity commuters would be just two minutes and no Virgin passengers would have to use buses.

However he admitted the effect on local trains would be significant, with travellers having to transfer to buses at either Cheadle Hulme or Colwich.

Best option

The closure is aimed at speeding up the West Coast Main Line upgrade which should allow Virgin's tilting trains to run on the line at speeds of up to 125mph by the end of 2004.

The Strategic Rail Authority (SRA) believes that doing the work this way will cause less disruption long-term than repeated temporary closures.

SRA chairman Richard Bowker said: "When completed, this massive engineering programme will bring the West Coast line up to the standard, in terms of capacity and line speed, required of a 21st Century high-speed rail link.

"It is time the industry got to grips with the challenges facing it. This programme is a good example of that."

Alistair Darling: "Upgrade is a necessary evil"

A thorough overhaul of the project will see the programme completed two years earlier than originally planned, Mr Bowker added.

Virgin runs trains between London and Scotland on the affected routes and also cross country services from places like Penzance and Bournemouth to Scotland.

A Virgin spokesman said: "This is a decision taken by the SRA, but we will do our best to minimise delays to customers."

Transport Secretary Alistair Darling said the track work was a necessary evil if the railways are to improve.

'�4bn saved'

He said: "This is a line that has needed investment for some 30 or 40 years now.

"We are finally getting control of the costs of the project.

"Chunks of the line will be taken out of commission totally because that will enable us to do the work more cheaply, because it is very expensive to have a series of very short stoppages."

Anthony Smith from the Rail Passengers Council said: "It's going to be very painful whichever way you do it, but we feel a short, sharp closure is much better than weekend after weekend, which is very inefficient.

West Cost main line upgrade

Originally estimated at �2.1bn Costs have reached �10-13bn Closures could save �4bn

"We just want to get the work done and get the new trains running."

The cost of the modernisation of the main route between London and Glasgow has become enormous - and it is way behind schedule.

The line is already being closed every weekend for 18 weeks for a 25-mile stretch between Milton Keynes and Hemel Hempstead.

The cost of the project is now put at up to �13bn, compared with Railtrack's original estimate five years ago of �2.1bn.

The SRA believes the line closures will cut about �4bn from the final bill, bringing the total budget "south of �10bn," according to The Times newspaper.

Public money

Taxpayers are expected to have to pick up much of the bill for Railtrack's failure to keep control of the project.

The huge cost over-runs were one of the main reasons for the government forcing the company into administration last October.

Since then, the SRA has also been forced to pay Virgin more than �100m from the public purse, to compensate for the delayed introduction of its new high-speed tilting trains.

Virgin says it will begin phasing its �1bn fleet of 53 new Pendolino trains into passenger service from the end of this year.

The company says they will probably run between London and Manchester at first, building up to a full, tilting service between London and Glasgow by 2004.