Lochshell Ltd was appointed to carry out the £1.3 million upgrade at the port earlier this year but restoration works were brought to a halt in June after it found the crumbling 17th-century port was in a worse condition than had been advertised.

Work resumed the following month after the contractor entered into talks with Aberdeenshire Council.

Now Lochshell workers have downed tools again with the contractor warning that repairs may not be completed until next summer – and at more than twice the original budget.

In a statement released exclusively to Aberdeen Journals, Lochshell claimed: “I am sure the famous civil engineer Thomas Telford, responsible for Banff harbour as one of jewels of the Scottish northern coastline, would be quaking in his grave at such damage to this historical listed structure without an appropriate design for repairs ready to be implemented.

“The contractor used leading survey techniques to present the site conditions, this should have been done by the client (Aberdeenshire Council) and these facts used to update the reality of the site conditions.

“The alarm bells are ringing already and then with the structure not repaired fully previously, or in advance of this contract, the voids in the structure allow significant volumes of water to enter the harbour and, even with substantial pumps running, make the working day challenging and restricted.”

Lochshell added: “Without the appropriate set of construction drawings the contractor and project are set to fail.

“It is the responsibility of Aberdeenshire Council as client to design and detail what it is that should be built – not the contractor.

“At this rate the project is on track to finish well over double the budget and may finish during 2022, somewhere between Easter and summer.

“This takes no account of the Scottish winter and weather conditions on this exposed site.”

An Aberdeenshire Council spokesman said: “We would like to reassure all Banff harbour users that our focus remains on completing these critical works as soon as possible.

“Whilst we are committed to completing this important project, it would not be appropriate to discuss contractual details publicly.

“We have requested urgent discussions with the contractor to find a way forward.”