The Enquirer has been contacted by a number of trade contractors who are reaching the end of their tether with construction corruption.

One said: “It’s just totally demoralising when you know you can do a good job but you don’t get near winning the work because the winner is decided on who hands over the biggest brown envelope.”

Subcontractors said the biggest problems are at site level where dominant project managers hold sway and chose suppliers who “look after them.”

One civils specialist said: “A lot of the time people further up the chain at head office have no idea this is going on.

“A persuasive project manager can be very powerful and it’s basically a case of look after him or you have no chance winning a contract on the job.

“We’ve lost major subcontracts to firms who are little more than a man with a van who divvy out the profits with the bent project manager.”

The boss of another civils firm said: “I’m fed up with it now. We’ve hung on for five years during the recession and now are losing work because we won’t pay backhanders.

“It’s not the sort of industry I want to be involved in.

“We need a proper look at this from the top and a few people to be made examples of.”

The problem is believed to be biggest on public sector civils jobs.

Another trade contractor said: “These jobs are supposed to be running cost effectively but there’s still a lot of spare cash for corrupt people to share out.

“Head offices and government ministers would be horrified if they realised the amount of money going into people’s back pockets on these sites.”