Sir Terry told BBC Radio 4 at the weekend that, despite his disappointment at setbacks to the scheme, “I am very confident that Crossrail has behaved properly”. There exist, he added, “plenty of documents that set out exactly what happened and when, and I do hope that these documents will be released soon for everyone to understand”.

Sir Terry said the documents demonstrate “very clearly” that Transport for London and the Mayor Sadiq Khan were told on 26 July that the Crossrail programme could not be delivered in 2018. “I spoke to the Mayor exactly along those lines,” he added.

This conflicts with the Mayor’s response to the London Assembly's Transport Committee regarding the delay, in which he claimed he was not informed of plans to put back the launch before the decision was taken by the Crossrail Board on 29 August.

Transport Committee chair Caroline Pidgeon said: “This ongoing situation is rapidly causing a loss in trust in the Mayor. If the Assembly was misled, that is a very serious breach of trust.”

She added: “It is quite incredible that we are yet to receive the Crossrail briefing papers. The longer the delay in delivering them the stronger the feeling of a cover up.”

A spokesman for Sadiq Khan said: “The Mayor has been clear that he discussed rising cost and schedule pressures with Crossrail over the summer, including looking at the implications if these issues weren’t resolved.

"At the meeting at the end of July it was clear that the opening date was at high risk of being missed but it was not until the end of August that the Mayor, Transport for London and the Department for Transport were told that the opening of the central section would definitely be delayed until Autumn 2019 – something the Mayor has not hidden his anger and disappointment about.”

Sir Terry Morgan also revealed to Radio 4 that he shortly expects to be dismissed from the High Speed 2 project, which he only became chairman of in August, due to Government frustrations at the Crossrail saga.

“I can only but assume, because I have not yet been told, that because HS2 is such a critically important programme, and with the sense of disappointment around the performance of Crossrail, that it was considered to be too risky for a programme like HS2 for me to continue in my role as chairman,” he said.

Crossrail is currently an estimated £600M over budget and services through central London are not now due to begin until next Autumn, having originally been expected to launch this month.

Photograph: Crossrail