Crossrail has filed its latest construction cost updates to Parliament showing the project has cost nearly £14bn to build so far up to the end of May.
Figures for the last year show £1.48bn was spent from May 2018 – May 2019 – which works out at more than £4m every day.
Crossrail bosses have outlined a six month “delivery window” for completion because “many risks and uncertainties remain.”
The earliest date is October 2020 and the latest March 2021.
That could mean another 20 months of construction work – which would cost another £2.4bn at current rates.
Network Rail has also been forced to increase its budget for Crossrail related work to £2.8bn.
Transport secretary Chris Grayling said: “The coming months will be critical for the project as Crossrail Ltd work to complete the installation and integration of the tunnel, stations and signalling systems, and Network Rail continue their works on surface sections of the route.
“It remains a hugely complex project and uncertainty and risk remains across the programme, with significant testing and integration work remaining.
“The new leadership team has committed to being fully open and transparent as it works through the final stages of the project, which is supported by the Department and TfL.”