London mayor Sadiq Khan has been accused of showing "incompetence" in his handling of the delay to the £15.4bn Elizabeth Line.
The London Assembly's transport committee branded Khan's response to a letter it wrote in October – in which it accused the mayor of misleading the public about the delay – as "wholly unsatisfactory".
On 31 August Crossrail announced that the Elizabeth Line, which will connect Reading and Heathrow in the west to Shenfield and Abbey Wood in the east, would be delayed until Autumn 2019 owing to delays in signalling testing.
At the time Khan said that neither he nor Transport for London (TfL) knew of the need for a new opening date until a meeting with the Crossrail board on 29 August.
In the October letter, first reported by City A.M., the assembly's transport committee challenged Khan's account, pointing to a number of meetings held between Crossrail, the Department for Transport (DfT) and TfL from 19 July in which they argued the delay would have been made clear.
Khan replied to the committee on 6 November and repeated his assertion that while he was aware of "significant growing cost and schedule pressures", Crossrail's position remained that the central section of the railway would open in December 2018.
He added: "It was Crossrail's responsibility to decide when the project schedule was no longer achievable, and they did not do this until the Crossrail board meeting on 29 August."
The mayor also denied the assembly's accusation that parliament and the London Stock Exchange had been misled through statements made by TfL on 24 July, which did not mention the delay. TfL has said previously that this is because it was not notified of the delay until 30 August.
The chair of the assembly's transport committee, Caroline Pidgeon, said Khan's response had left it "wanting".
“Simply accepting Crossrail’s assurances about the launch date seems to show incompetence, or at the very least, disinterest," she said.
The committee said the mayor failed to provide it with crucial details such as the revenue impact on TfL, potential penalty notices and revised opening dates for the eastern and western sections of the line.
Khan's deputy mayor for transport Heidi Alexander said the committee's criticisms were "nonsense".
"The mayor has always been clear that he had discussed rising cost and schedule pressures with Crossrail Ltd over the summer, but it was not until the end of August that he was told that the opening of the central section was being pushed back to autumn of next year.
“In every project of this size, there are always risks that are being managed and both the mayor and TfL were relentless in questioning Crossrail Ltd on their assumptions and their actions every step of the way."
TfL and Crossrail declined to comment.
Late last month the government bailed out Crossrail with a £350m loan. Shortly after Crossrail chief executive Simon Wright announced he will step down from his role later this year, to be replaced by London Underground managing director Mark Wild.