A COMMITMENT to building a high-speed rail line in Scotland, slashing train journey times to London, will form the centrepiece of a 20-year investment plan unveiled by the Scottish Government today.

Alex Neil, the Cabinet Secretary for Infrastructure, will confirm that ministers intend to fund a 250mph line starting in the Central Belt at the same time as work takes place on a new fast route in England.

It follows concern that Scotland has so far been sidelined from the high-speed rail revolution that has promised to transform intercity travel in England.

The announcement marks a major policy shift for the Scottish Government, which had previously complained about the time it would take for a route to reach Scotland after starting in the UK capital.

However, work on a Scottish leg is only likely to get under way after 2025, as money has already been earmarked for dualling the remainder of the A9 between Perth and Inverness.

High-speed rail is due to be among more than 80 major projects and programmes published today as part of an updated Infrastructure Investment Plan, Government sources said.

Scottish passengers are expected to see only marginal time savings when a planned link between London and Birmingham, the first phase of a £32 billion project, is completed in 2026, as they will continue north on conventional track.

Glasgow and Edinburgh are the cities in Scotland most likely to benefit from today's announcement, while the overall boost to the Scottish economy could be up to £25bn.

As part of its preparation for including Scotland in the UK high-speed network, Mr Neil will ask for High Speed 2 (HS2), a company set up by the Department for Transport, to draw up detailed route options for Scotland.

The company is currently working on plans for a second phase of high-speed rail which would see branch lines built from the Midlands to Manchester and Leeds.

However, it is not yet clear what route any Scottish line would follow, as this depends on how plans progress in England, with a decision on the first phase of the project delayed until January amid concern from Tory backbenchers in the Chilterns.

Among the options being explored are an east coast route to Edinburgh, a west coast route to Glasgow or a Y-shaped alignment that splits in southern Scotland with branch lines to serve both cities.

A spokesman for the Scottish Government said: "We have long been pressing the case that it is vital for a high-speed rail network to be established across Britain. We are ready to start preparatory work and we have already asked the Secretary of State for Transport that the remit of HS2 Ltd is extended to include detailed planning for routes to and within Scotland.

"Our Infrastructure Investment

Plan, setting out our ambitious programme for investment across Scotland, will be published on Tuesday. The full contents of our extensive plans will be made public at that point."

It is thought the network would see journey times from Scotland to London of less than three hours, making train travel more attractive than flying.

HS2 will also be asked to look at options for building new terminals in Glasgow and Edinburgh as the stations currently in place are thought unlikely to manage the additional services that high-speed rail will bring.

The announcement follows the establishment of a Scottish Government-led working group in June to advance the case for Scotland's inclusion in a high-speed network.

Garry Clark, head of policy at the Scottish Chamber of Commerce, said he welcomed ministers' commitment to building high-speed rail infrastructure in Scotland.

He said: "The last infrastructure investment plan, in 2008, had a 10-year vision. We have been arguing that the Government should move beyond that kind of short-termism and look at aspirational funding for putting a line in place. It could be 15 or 20 years but if the plan is there and we're seeing progress towards it, we're comfortable with that."