It was confirmed last week that the project will be at least nine months late.
But contractors have been pouring resources into the scheme for months as Crossrail leaders hoped to meet the original deadline.
Now site sources claim the builders’ extra costs will come under intense scrutiny after the completion race was lost.
One said: “It was like money was no object when everyone was racing to meet the original deadline.
“But now that has been pushed back the world has changed.”
Another added: “Some daft things have been happening in terms of money spent down there and now the bills are going in they will be getting a proper auditing.
“There’s a major row brewing between the contractors and Crossrail over the extra costs that have been ramped up.
“As usual I fear it will be the supply chain that gets shafted.”
The Enquirer understands that among the extra resources a fortune has been spent on drafting in teams of additional engineers.
One source said: “Loads of them were coming in on £500 a day which had to be matched for the existing engineers who got the hump.”