The firm revealed that it had received 478 signed contracts in the post by the start of the year from 1,250 staff who were asked to sign the new Building Engineering Services National Agreement contract.

Mechanical and electrical staff at eight leading building services contractors have been given until Monday to sign the new agreement.

After electricians will work through their individual contract notice periods before leaving employment.

Balfour said it expected to see a flurry of contracts arriving in the remaining days.

A spokeswoman for the contractor said: “We expect that over the next few days more signed contracts will be returned as the postal service returns to normal and employees resume working after the holidays.”

Following this date those employees who have not returned their contracts will be invited to a one-to-one meeting to understand their remaining concerns.

She added: “The positive response to signing contracts demonstrates that our employees understand the importance of the BESNA to our business and industry as a whole.”

The major M&E firms asking workers to sign new contracts are:  N G Bailey, Balfour Beatty Engineering Services, T Clarke, Crown House Technologies, Gratte Brothers, MJN Colston, Shepherd Engineering Services and SPIE Matthew Hall.

HVCA chief executive Blane Judd said: “We are expecting to hear more good news from the other contractors in the next few days.

“We are encouraged that the people that this agreement really affects have taken time to look at the issues and are reacting positively.”

Union Unite is understood to be planning a day of action by electricians on Monday to mark the deadline for signing up to the new contract.