A report by the watchdog noted that “no action was taken to deal with any potential contamination of the area or the individuals” after the hazardous material was disturbed at Bridge of Don Academy in July.

It took a further five days before action was taken to inform the action control team.

During this period there were a “significant number of people working in and transiting through the area” before the doorway was sealed-off.

The HSE has now written to the local authority after its investigation.

The letter said an apprentice joiner removed an insulation board from above a doorway as part of the work to move the position of the door.

Having removed the board by using a hammer and chisel, he realised that it may be asbestos-containing material and alerted his supervisor.

The broken board was double wrapped in plastic and placed beside the skip, and a further piece of board - still above the door and intact - was covered using a ceiling tile and cardboard.

An email was sent to the architect requesting a sample be taken as asbestos was suspected. No action was taken to deal with any potential contamination of the area or the individuals.

When the remaining board was sampled five days later the asbestos officer indicated he thought it was asbestos-containing material.

It was only at this point that the risk control team were informed and the fact that there was broken material came to light.

The council has been given until December 20 to act on all the findings.

The Unite union said the major breaches occurred despite it repeatedly raising concerns with the council’s senior officials over the previous 12 months when other management of asbestos related incidents had occurred.

Regional industrial officer, Tommy Campbell, said: “The report on the asbestos incident at the Bridge of Don Academy is absolutely scathing. The procedures put in place to deal with potential asbestos material were woeful, and in fact represented a threat to public safety. Unite has repeatedly raised our concerns that exposure to asbestos is not being robustly and strongly responded to when incidents occur in line with health and safety procedures. It’s our belief that the Bridge of Don Academy incident is not a one-off but symptomatic of a casual approach to the safety of workers and the public.

“Aberdeen City Council clearly requires an investigation into its health and safety procedures, whether they are the best placed to do this in light of this evidence is highly debatable to say the least.”

Unite raised a Freedom of Information (FOI) request on August 28 with Aberdeen City Council in response to a number of the recent asbestos incidents at the Bridge of Don Academy, Hazelwood Academy and at residential properties.