The two parties are at loggerheads over Laing O’Rourke’s decision not to allow union officials access to the new hospital for NHS Scotland, claims which have been refuted by the contractor.

UCATT regional secretary Steve Dillon met Trevor Donoghue, Laing O’Rourke’s industrial relations manager, on Wednesday to resolve issues, though Mr Dillon described the meeting as “short, sharp and volatile”.

The meeting was arranged after UCATT held a series of protests earlier this month outside the Dumfries site.

Mr Dillon said he was told that the only access Laing O’Rourke was prepared to provide was that union officials could speak at some inductions, with management in attendance, and then hand over any literature to the company for distribution.

When UCATT raised the possibility of speaking to workers freely in canteens and rest areas not in the presence of management, Mr Donoghue told the union that form of access would not occur.

Mr Dillon said: “Laing O’Rourke have learned nothing from the blacklisting scandal. They want to intimidate workers not to join the union and if someone shows any interest then they will be marked as a target from day one. This is backdoor blacklisting and can’t be tolerated on a public sector project.”

According to UCATT, the company’s refusal to allow access to the site is contrary to the Scottish Government’s Fair Work Convention.

Mr Dillon added: “We don’t want favours, just fairness and the ability to speak to workers freely without fear of retribution. If the Fair Work Convention means anything then the Scottish government must take action to force Laing O’Rourke to provide proper access.”

Following initial UCATT protests, Colin Smyth MSP tabled a parliamentary motion condemning Laing O’Rourke’s action, which has so far received the support of 14 of his colleagues.

“This issue will not go away,” Mr Dillon said. “The campaign to win access from Laing O’Rourke will be ramped up over the coming months.”

The hospital is due for completion in December 2017.