Sadiq Khan only learned of Crossrail’s delay two days before the announcement, he told the London Assembly.
The London Mayor said he was informed on August 29, following a decision by Crossrail Ltd on that day.
It was announced on August 31 that the capital’s new east-west railway would open in autumn 2019 rather than December this year.
In a meeting at City Hall, Mr Khan was asked by London Assembly chairman Tony Arbour if he had been “kept in the dark over the matter”.
Mr Khan replied that the progress of the project has been on the agenda of “every single Transport for London (TfL) board meeting” and “throughout the last year … some challenges facing Crossrail have become clear”.
He added that he was “extremely disappointed, frustrated and angry by the delay”, but believes the railway will be “an amazing feat of engineering and a great asset” once it opens.
Sir Terry Morgan, chairman of Crossrail Ltd, told Assembly Members (AMs) that the firm’s executive committee “raised concerns” about progress at a meeting on July 19 but decided to investigate the issue further.
He insisted that at that time “we were still working against a programme that supported a December opening”.
Conservative AM Keith Prince accused Sir Terry of giving “no indication whatsoever that there would be a delay” at a meeting attended by the pair and Members of Parliament on July 23.
Sir Terry insisted that he “was not dishonest” and claimed it was “the right thing to do to get the executive to conclude their work in a proper way”.
MPs were “very surprised and disappointed” that they were not told that a delay was a possibility, Mr Prince added.
Crossrail Ltd confirmed on August 31 that more time is needed to complete the railway’s infrastructure and testing.