The Enquirer understands that an army of workers is still needed to complete the project which is being “flooded” with operatives.

Internet jobs boards are full of vacancies for M&E workers on the project.

A source said: “That’s just the tip of the iceberg.

“Most recruitment is word of mouth and referrals and they are absolutely flooding that job with anyone they can get.

“I can only imagine what the cost will be but they are offering top dollar.

“The final bill is going to be massive and I doubt anyone really knows the numbers.”

Crossrail confirmed a nine month opening delay last month.

It said: “The original programme for testing has been compressed by more time being needed by contractors to complete fit-out activity in the central tunnels and the development of railway systems software.

“Testing has started but further time is required to complete the full range of integrated tests.

“Construction activity is drawing to a close including the completion of the remaining architectural fit-out in the new central section stations.”

A project source said: “The ATC joint venture (Alstom, TSO and Costain) has been instructed by Crossrail to  carry out train testing to verify the signalling.

“Of course that’s necessary but it creates its own problems when the fit out work isn’t complete.

“When trains are sent through the tunnels, nobody can work so we have to stand the guys down.

“It’s a long way from being finished and the train testing is having a major impact leading to people being forced to sit around doing nothing rather than getting on with the job.”