Shares in the construction and services firm fell 38% last month after it warned operating profits in the second half would be around half that reported a year ago amid “further deterioration” in UK construction and support services.

The Interserve Board had admitted to “a realistic prospect” of the group breaching its financial covenants with lending banks.

The Construction Enquirer has now reported that letters were sent out last week to workers whose jobs are now at risk.

Jobs under threat are believed to be management and back office roles.

An Interserve spokesperson told Construction Enquirer: “Since October this year, we have been reviewing our business strategy and performance to create a stronger platform for Interserve’s future profitable growth.

“In the short term, we are reducing the overall costs within the business, and this will unfortunately have a direct impact on some of our people with possible job losses.”

The UK’s largest construction union Unite has called for employers at Interserve to meet with the union and discuss the company’s future.

Unite national office for construction, Bernard McAulay, said: “It is vitally important that Interserve sits down with Unite and explains fully what is going on at the company and what the plans are for the future.

“There are many Unite members currently employed with Interserve in construction roles who are becoming increasingly concerned about the uncertainty which is currently surrounding the company.

“It is not acceptable for Interserve to hold Unite at arms-length and to deny us a seat at the table when workers’ jobs are under threat.”

“Workers need reassurance that there are not going to be further job losses in the short to medium term.”