TRAIN delays on Scotland's busiest rail route could become far worse after a decision to scale back a £1 billion investment programme, senior industry figures have warned.

Revised plans to electrify the line between Glasgow and Edinburgh were branded "potentially disastrous" yesterday as it emerged that electrification of alternative routes used when problems hit the main commuter route had been mothballed.

It is claimed passengers could be left waiting hours for the route to be re-opened in the event of glitches with trains, infrastructure or weather affecting the main line via Falkirk.

The Edinburgh Glasgow Improvement Programme (EGIP) has seen its budget slashed from £1bn to £650 million and the electrification of more than 200 miles of track in the central belt cut by 50%.

Senior planners said the loss of diversionary routes from Greenhill Junction to Polmont via Falkirk Grahamston and Winchburgh to Edinburgh via Dalmeny – which would not be available to electric trains – could have a significant impact on performance.

A senior figure told The Herald: "There is a significant performance risk. If you have a problem on the route, the trains would sit still while it is fixed. It can take five to six hours to fix an overhead line fault. The only thing you could run during that time is diesels but all the electric trains would be standing all over the place because you couldn't move them.

"You can run diesels but where are the diesels coming from? They're going to be cascaded off from E&G because you can't afford to have them sitting in the sidings. The performance could be potentially disastrous. You could have people sitting there for hours."

The decision to indefinitely postpone electrification of the line to Stirling, Alloa and Dunblane would also create problems for passengers travelling between Glasgow and Edinburgh as electric trains would no longer be available to provide cover, it was claimed.

Another source said: "There's absolutely no point in electrifying Edinburgh to Glasgow unless you electrify the diversionary routes."

Details of the cuts were still being clarified yesterday, with officials from Transport Scotland, the Government agency funding the project, briefing counterparts at rail infrastructure operator Network Rail about which routes would no longer be electrified.

A spokeswoman for Transport Scotland dismissed concerns about delays. She said: "The statement about five to six-hour delays is utterly fictitious with absolutely no supportive evidence. The Airdrie to Bathgate route offers an already constructed electrified diversionary route. We are already working with ScotRail and Network Rail to develop a robust contingency plan that deals with delays along the route."

Network Rail said it remained committed to improving the punctuality and reliability of train services. "The electrification of the lines to Falkirk Grahamston and Dalmeny is not part of the current EGIP specification, but they could be electrified in future phases as the Government has committed to funding 100 kilo-metres of electrification each year following the completion of EGIP," a spokesman said.

Robert Samson, Scotland manager for rail watchdog Passenger Focus, added: "For the EGIP programme to be successful it has to deliver on enhanced punctuality and reliability for passengers."

Figures published yesterday by Network Rail show that 94% of ScotRail services were deemed to have arrived on time in the four-week period to June 23, up from 92% a year earlier.