Firms said they are powerless to follow Nichola Sturgeon’s political call for works to stop because of the failure of local authority clients to instruct them to close sites.

One major contractor, who asked not to be named, said: “We’re caught between a rock and a hard place. The public and unions are berating us for continuing to work, but we can’t stop without our client’s say-so. It would leave us wide open to delay notices and end in protracted disputes in the courts.

“It an impossible situation at present.”

Union Unite condemned Morgan Sindall over the weekend for planning to resume work on the high-profile £250m Sighthill regeneration project for Glasgow City Council.

Pat Rafferty, Unite Scottish Secretary, said: “It’s absolutely staggering that the Sighthill regeneration project is scheduled to re-open on Monday.

“The Scottish Government’s instruction is not being adhered to and tougher measures must be brought forward with immediate effect.”

Now the Scottish Government has pledged to intervene and said it would contact Morgan Sindall to stop works this week.

Despite a clear statement from Scottish leader Nicola Sturgeon last week, there has been a mixed response from clients so far.

Edinburgh City Council took the decision to instruct contractors Morrison Utility Services  and Sacyr Farrans Neopul to cease site works on the Edinburgh tram project last Thursday.

But contractors are still working for various public procurement Hub Companies across Scotland because they have not received instructions to stop.

One Hubco spokesperson confided that they were still working through the process and had to consult with various local authority clients before halting site work.

The Scottish Future Trust, which oversees Scotland’s five Hubcos said that hub companies would be following  Scottish Government guidance.

David MacDonald, hub programme director at the Scottish Futures Trust, said: “The health and safety of all employees across the hub programme is of paramount importance to us.

“The five hub companies are following government guidance and can confirm that all non-essential construction sites have closed down or are in the final stages of being closed down.”

He added: “A number of sites have been classified as essential by contracting authorities and work will continue while safe operating procedures and social distancing measures are in place.”