Further delays to the long awaited Aberdeen Western Peripheral Route have been revealed in the Scottish Parliament, with completion not now expected until December at the earliest.

Scotland’s Cabinet Secretary for Transport, Infrastructure & Connectivity Michael Matheson told MSPs that defects to a structure crossing the River Don require more work to repair than initially thought.

This latest delay puts the scheme’s full opening back an entire year from the winter 2017 / 18 completion date targeted at the start of works.

Technical issues on the Don crossing were first reported by contracting consortium Aberdeen Roads (ARL) in May, by which time poor weather and the collapse of consortium partner Carillion had already set back the planned opening to late Autumn.

The defects – identified when post-tensioning a number of concrete panels cladding the structure – subsequently proved to be more extensive than initially believed but were not expected to further affect the opening date.

However Transport Scotland has now been informed that a December completion is likely due to a greater scope of work being needed to repair the defects. Michael Matheson said no firm opening date could be confirmed.

“We will continue to work closely with ARL to ensure that everything that can reasonably be done is being done, and we will provide a definitive date for the opening of the section as soon as possible,” he told MSPs.

“Although the issues reported require time to remedy, it is important to recognise that they were found because of the rigorous quality control and design checks that have been built into the project. It is also important to note that the costs of the repairs lie with ARL and will not impact on the public purse,” he added.

The Cabinet Secretary also said Transport Scotland has been working with ARL to identify whether a 31.5km section of the new road from Craibstone to Stonehaven and Charleston could be opened early.

This, he explained, would require a variation to the original contract, which he claimed the contractor has agreed to discuss with its lenders. However Michael Matheson said such discussions have still not taken place and expressed disappointment at the lack of progress towards a “mutually beneficial solution”.

“It is now time for the contractor to stop deliberating and start acting,” he said. “It must now take the necessary steps to open the majority of the road and let the people of the North East enjoy the benefits that they have been so patiently anticipating.”

When approached for a statement, an ARL representative said that due to the partnering nature of the Aberdeen Western Peripheral Route project it was unable to comment. ARL is a joint venture comprising Balfour Beatty and Galliford Try.

Responding in Parliament, Conservative MSP for North East Scotland Liam Kerr expressed doubt as to whether the road would be fully open in December. He said the Scottish Government should have predicted the issues and delays “months ago” and made provision, adding that it is “a disgrace” it has failed to do so.

Michael Matheson said: “The reality is that when dealing with such a project – the road is some 58km long and has more than 100 different structures on it – it is difficult to anticipate every technical issue that might arise. It is a major infrastructure project, and there will always be challenges and technical issues with major infrastructure projects.”

 Some sections of the scheme have already opened to traffic including a 7km stretch between Blackdog and Parkhill and a 12km route from Balmedie to Tipperty.

 Photograph: Transport Scotland