The soon-to-be sacked HS2 chairman Terry Morgan has insisted he told Sadiq Khan that the £15.4bn Elizabeth Line was not going to open on time at least a month before the London mayor said he knew about the delay.
Morgan, who has led the Crossrail project for a decade, told the BBC that he was in "absolutely no doubt" that Khan was told on 26 July that it was no longer feasible to deliver Crossrail, also known as the Elizabeth Line, in 2018.
The Elizabeth Line, which will stretch from Heathrow in the west to Abbey Wood in the east, was due to open on 9 December but was pushed back to next year due to issues with signalling testing.
The mayor has maintained that he was not told there would be a delay to the project until two days before the announcement.
The squabble between Transport for London (TfL), which Khan chairs, and Crossrail came to a head this summer when the London Assembly accused the mayor of "misleading" the public about what he knew about the delay.
The mayor maintained that while he was informed of cost and time pressures in July, it was not until 29 August that he was told the railway would need a new opening date.
This morning chair of the Assembly transport committee Caroline Pidgeon was asked whether she believed Morgan or Khan.
She replied: "I have to say I believe Terry Morgan in this instance. It's quite clear the mayor was briefed in July, and if you are told that a project, a very high profile project, is at high risk of not opening in the year it was supposed to, you would know about it and to try to pretend you didn't know anything until a day before the public knew at the end of August is not feasible. It says you are not on top of the job or you are not taking on board what officers are telling you."
She said the project's delay mattered because it was going to form the model for other projects going forward.
Pidgeon added that there was the potential that markets could have been misled when they received a statement from TfL in July that made no mention of the delay.
Pidgeon has already written to the financial watchdog, the Financial Conduct Authority (FCA) to ask it to investigate the delay.
Last week Morgan told Sky News that he expected to be fired as chairman for HS2 – a position he has held since August – owing to the problems with Crossrail.
As the end of September the mayor and TfL commissioned a governance report into the Crossrail delay, which is currently ongoing.
TfL said in a statement to the BBC: "At the meeting at the end of July it was clear that the opening date was at high risk but it was not until the end of August that the mayor was told the opening would definitely be delayed until Autumn 2019."