A railway link upgrade between Aberdeen and Inverness has been delayed – and almost doubled in cost.
The infrastructure project was due to be completed by March 2019, with a price tag of £170 million.
But a report by Transport Scotland reveals the bill is now set at £330m, with delays caused by the rise in cost setting a new finish date of September that year.
The details were put before the North-east’s transport body Nestrans on Friday with no explanation for the price hike.
Councillor Martin Ford, who sits on the board, said: “The scale of the increase in the projected cost of the Aberdeen-Inverness rail line upgrade is astonishing, especially since the work has already started. What has changed?
“Or was the previous estimate wrongly calculated? Or why have anticipated prices risen so drastically?
“We need to have an explanation.”
The improvements will allow for a half-hourly commuter service between Aberdeen and Inverurie, as well as peak services between Moray and the Highland capital.
A Scottish Government spokeswoman said the increased costs set out by contractors BAM Nuttall would be challenged and they called on the UK Government to devolve more network management powers.
She added: “We have warned repeatedly that there need to be fundamental changes in how our railways are run.
“Time and time again we have set out a full and compelling case to the UK Government for the full devolution of Network Rail to Scotland.
“Time and time again these requests have been rejected.”
The Nestrans board asked director Derick Murray to write to the Office of Rail and Road seeking an explanation for the huge cost increase.
Rail Minister Paul Maynard said there were no plans to further devolve networks. He added: “We are committed to working closely with the Scottish Government to provide a better railway for passengers.”