London's Crossrail line will not now open next year - and its cost will rise again by up to £650m.
Mark Wild, CEO of the firm building the east-west railway, said today that services on the already-delayed line will start "as soon as practically possible in 2021".
And Mr Wild said the total cost of the project, which will be known as the Elizabeth Line, could reach £18.25bn - up as much as £650m on the most recent funding commitment from December.
The budget was originally set at £15.9bn in 2007
Crossrail, which is being funded by the Department for Transport and Transport for London, was originally set to open in December 2018. In April it was announced that the railway should open between October 2020 and March 2021.
Mr Wild said he wanted to "ensure reliability of the railway from day one of passenger service".
He added: "We are doing everything we can to complete the Elizabeth Line as quickly as we can but there are no shortcuts to delivering this hugely complex railway.
"The Elizabeth Line must be completed to the highest safety and quality standards."
Caroline Pidgeon, who chairs the London Assembly's Transport Committee, said: "The further delays to the opening of Crossrail and increasing costs are appalling news for Londoners.
"The delay creates huge issues for many businesses that have made investment decisions based on its original opening date of December 2018."
Crossrail said there were four "major tasks" that must be completed before services can start. They are:
- Build and test the software to integrate trains with three different signalling systems;
- Install and test station systems;
- Complete installation of equipment in the tunnels and test communications systems;
- Trial run the trains for thousands of miles.
