Work on the Aberdeen bypass was halted for nine days after a “safety incident” on the £745million project.
It has emerged that the problem happened on October 24 last year and is believed to have involved an issue with on-site equipment.
It did not cause any injuries to workers, but was the catalyst for nine days of “down time” as the contractors, Aberdeen Roads Ltd (ARL), attempted to work out how to avoid any repeat.
Transport Secretary Michael Matheson was last night urged to explain “exactly what happened”.
The incident has only come to light after minutes were published from a meeting which Mr Matheson held with ARL bosses on November 8.
A “robust” conversation was described between those present as they discussed the timetable for opening the Aberdeen Western Peripheral Route.
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The redacted minutes also show that the SNP minister was told by Balfour Beatty chief executive Leo Quinn at the time that a December opening was “only one scenario”.
Mr Quinn also suggested that Galliford Try chief executive Peter Truscott would not have suggested a December 8 completion date if he had known about the safety incident.
The southern section of the bypass opened last month, but the full road is still to be completed because of an issue with a new bridge over the River Don.
Liam Kerr, Scottish Conservative MSP for the north-east region, said yesterday: “This is yet another example of the SNP trying to keep problems with the AWPR under wraps.
“There has been a total lack of transparency from the Scottish Government throughout this process.
“These minutes suggest that workers downed tools for almost two weeks at the end of October.
“The transport secretary should explain exactly what happened and update parliament on when we can expect full completion of the road.”
North-east Labour MSP Lewis Macdonald said: “A safety incident requiring nine days’ down time to address sounds quite significant.
“If even CEOs don’t get told about such incidents, it is little wonder that Transport Scotland seems to be so often out of the loop.”
A Transport Scotland spokesperson said: “The minutes show why the cabinet secretary has been right to advise caution regarding the contractor’s programme.
“ARL has confirmed it is continuing to target this month (January) for the opening of the Don Crossing, subject to the impact of adverse weather.
“The series of technical issues which the contractor faced during the construction of the Don Crossing is well documented.”
An Aberdeen City Council spokeswoman said: “There has been a review of the city’s directional signs that are affected by the opening of the AWPR and the de-trunking of parts of the network. The amendments to the signs will be undertaken over the coming months.”