Long-distance ScotRail passengers may have to travel in unrefurbished second-hand trains because of further delays to their overhaul.
They would have to be pressed into service in December as part of the operator’s biggest increase in services for 25 years, The Scotsman has learned.
The 40-year-old trains should have started on routes such as Aberdeen-Edinburgh in May.
However, the first of the 26 trains, previously operated by Great Western Railway in England, is not expected to carry passengers until next month.
ScotRail needs ten for the extra services and expects it will have to use up to nine unrefurbished trains being used to train drivers.
Managing director Alex Hynes said: “We will struggle to have the trains by December. [Refurbishment firm] Wabtec’s delivery has been dreadful.
“The amount of work needed has been more than they budgeted for.
“We may have to operate them in ‘classic mode’ - in an unrefurbished state.”
However, he said passengers would prefer that to keeping the current trains because they were more comfortable, smoother and quieter.
Mr Hynes said “Customers in the Highlands love them” - referring to similar trains that LNER operates between Aberdeen, Inverness and London.
He said: “They have a more relaxing atmosphere and you don’t have a diesel engine beneath your feet.”
Mr Hynes said the refurbished versions would be “fantastic -, really high quality.”
The Scottish Liberal Democrats condemned the further setback, which follows delays to ScotRail’s brand new electric trains.
Transport spokesman Mike Rumbles said: “We’re already well behind in the introduction of the new electric trains and now we are told the upgraded trains on Scotland’s long-distance routes are also languishing in a yard not ready for action.
“The public ought to be able to expect better than temporary stop-gap solutions.
“ScotRail and its contractors have a battle ahead to convince customers that delivering the service passengers expect is a priority for them.”