A number of specialists have been in touch with the Enquirer to voice their concerns over deteriorating relationships.

One said: “It’s like these QSs are making bonuses on the back of how much they can scalp off us.

“It’s pretty depressing at the moment. There’s certainly a new breed of younger QS who are drilled by the main contractors to get back what they can.

“We’ve had QSs say things like ‘it’s only 50 grand.’. That’s easy to say when you work for a major contractor and it’s not your money.”

Specialists said members of main contractor approved supply chains are bearing the brunt.

Another subcontractor said: “Being a member of the supply chain was supposed to be all about good relationships but some main contractors think they can screw us at will now.

“Some firms are worse than others and a lot of suppliers are refusing to work with those with the worst reputation.”

One specialist boss said: “We had a £450,000 package with one firm and at the last minute the QS tried to knock £75,000 off with all sorts of spurious claims.

“It’s a joke really. We all know margins were mega tight a few years back but this is now happening on jobs the big contractors are supposed to have bid at more realistic prices.

“They just see the supply chain as a way of boosting that margin and the QS team is on the front line doing that.”