London's top transport boss should consider quitting, a report into Crossrail's delays has recommended.
The project, to build a new railway underneath central London, was due to open in December 2018 but it might not open until 2020 at the earliest.
A report by the London Assembly has recommended Transport for London (TfL) commissioner Mike Brown reflect "on whether he is fit to fulfil his role".
TfL said the project's delay was down to the previous Crossrail management.
A spokesperson for London Mayor Sadiq Khan, who is responsible for the transport authority, said the mayor had "every confidence" in TfL's commissioner.
Mr Brown has not yet commented but a spokesperson for TfL said the commissioner had kept the mayor informed of all of the project's developments.
Construction work for the project began in May 2009, with tunnelling commencing in May 2012.
However, the scheme has come under increasing pressure as its costs have increased.
Three emergency cash injections have seen the cost of the route rise from £14.8bn to £17.6bn, with the first rise revealed in July 2018.
The report claims warnings the project would not open on time were downplayed by Mr Brown.
It also concluded better scrutiny was needed of the governance of the project as well as assurances people with the correct skills needed were in place.
A corporate culture of transparency should be instilled and the "overly optimistic corporate culture" needed to be kept in check by independent reviewers.
It added future infrastructure projects should strive to keep designs simple rather than include bespoke features in order to reduce risks to the budget and timelines.
Chair of the Assembly's transport committee, Caroline Pidgeon, said: "It is frustrating that top Crossrail executives have not taken responsibility for their mismanagement of the project in its later stages.
"This despite the fact that they were taking home eye-watering salaries and bonuses to deliver the project."
What is Crossrail?
Crossrail is a new railway that will run beneath London from Reading and Heathrow in the west through central tunnels across to Shenfield and Abbey Wood in the east.
Construction began in 2009 and it is Europe's biggest infrastructure project - it had been due to open in December 2018 although last summer that was pushed back to autumn 2019.
It has been officially named the Elizabeth Line in honour of the Queen and will serve 41 stations.
An estimated 200 million passengers will use the new underground line annually, increasing central London rail capacity by 10% - the largest increase since World War Two.
Crossrail says the new line will connect Paddington to Canary Wharf in 17 minutes.