Chief executive Mark Wild told spending watchdog MPs that the project would not be completed this year, and added he sincerely hoped it would be completed in 2020.

Wild told Public Accounts Committee MPs that his team had spent two months unravelling the knots in the ‘compressed’ project and building a new logical sequence of work to complete the project.

He said he would now start four weeks of talks with Tier 1 contractors to verify whether the productivity assumptions on the new plan were valid and deliverable.

Wild said that next month Crossrail would set out its plans to complete the project within the new planned cost envelope of £18bn, rather than £15bn as previously planned.

He said: “We will present a window  – it won’t be a definitive date because there is still a lot of uncertainty – but we will have a window when this railway will open.

“There is no opportunity to open this railway in 2019 because of the various compressions of both the critical path stations and the signalling systems.

“We very much want to get this done in 2020.”

He added that if the stations had held their original programme the original December 2018 project opening date would have been achievable.

“But when the railway stations started to slip in 2016/17 we should have paused for breath and resequenced the programme,” he said.

“At that point, the racheting effect of systematic risk was building up because really you want the stations finished before you put the train through the tunnel”

“It is now likely we will finish the railway systems before the stations,” added Wild.