The cost of Crossrail has risen by around £590 million to £15.4 billion, UK rail minister Jo Johnson has revealed in a written statement to parliament.
Increasing cost pressures across the project have been blamed for the increase.
However, Johnson was quick to point out this figure is below the previous estimate of £15.9 billion as calculated in 2007, as well as the £17.8 billion from 2009, which prompted a spending review.
Of the extra £590 million being allocated to the megaproject, £300 million is being made available to Crossrail Ltd, with joint sponsors the Department for Transport (DfT) and Transport for London (TfL) contributing £150 million each.
In addition, around £290 million is being provided for completion of the programme of works on the national rail network, and is being funded by the DfT and Network Rail.
Figures up until May 2018 show that £12.5 billion has already been spent on the project.
Work on Crossrail, which will become the Elizabeth line when services begin in December, has now reached 93 per cent completion with testing and commissioning taking place.
All core track work is finished but construction and fit-out of the new Elizabeth line stations, excluding Abbey Wood which is already open, continues to progress with the installation of lifts and escalators and completion of architectural finishes.