The line had been due to be shut between Dalmeny, at the southern end of the Forth Bridge, and Haymarket in Edinburgh, for preliminary work ahead of electrification of the route. Buses would have replaced some trains, with services between Edinburgh and Aberdeen diverted via Stirling.
Industry sources told The Scotsman the closure period had been chosen as the least disruptive to passengers as it has traditionally been one of the quietest times of the year. No new dates for the work have been chosen.
It is understood that transport minister and Fife MSP Jenny Gilruth ordered the project to be put back within the past two weeks, despite planning for it starting more than a year ago and being agreed in July. One train operator said the decision had come after timetables for the period were published.
The Scottish Government’s Transport Scotland agency said: "While these works were initially suggested for the festive period, Fife rail users have already made their dissatisfaction with the ScotRail service clear. Therefore we will ensure the significant investment in the planned electrification works brings little or no disruption during the seasonal holidays.
“Travel patterns have changed post-pandemic and it is with this in mind that the rail industry needs to rethink its traditional approach to carrying out engineering works during holiday periods such as Easter and Christmas. Our key aim in bringing ScotRail into public sector control is to put the passenger first and this includes putting their needs foremost while planning and delivery of engineering works.
"We have also challenged [track owner] Network Rail to provide robust forward plans that sets out considerations, including detailed costings, for disruptive engineering works given the changes in travel patterns.”
The agency said it was too early to say when the work would be done instead. However, it sought to reassure rail engineering contractors that it would strive to ensure they had a “reliable stream of work” under the changing approach to scheduling such projects.
One rail source said the industry was “frustrated and a bit angry” at the late-notice change, with preparations estimated to have cost several million pounds.
A Network Rail spokesperson said: “We work closely with our industry partners to plan our engineering programme and decided not to deliver works which had initially been scheduled for the Dalmeny corridor between Christmas and New Year.”
The body said it had been planning to carry out some bridge works, but had not entered into any contract for the work and “did not progress with the works following consultation with our industry stakeholders, including Transport Scotland”.
Passenger watchdog Transport Focus welcomed the postponement. Senior stakeholder manager Robert Samson said: “Rail travel has been disrupted for passengers over the festive period for the past two years. This change will be of benefit to passengers travelling over the festive period.
"It’s important that disruptive engineering work is designed to keep passenger inconvenience to a minimum that takes full account of changing travel patterns.”