Up to 1,400 job losses are planned at Transport for London (TfL) including in engineering and on the London Underground, according to the Rail, Maritime and Transport (RMT) union.
The RMT said the jobs are at threat due to spending cuts.
Mick Cash, the union's general secretary, said:
As part of the mayor's efforts to slash spending by £ 5.5bn by 2021 we are now being told that the company plan to cut up to 1,400 jobs in engineering in TfL and in some areas of London Underground.
RMT demands that no cuts take place, so close to the King's Cross fire anniversary it would be appalling if there was any hacking back on safety.
The mayor needs to stand up for TfL and demand restoration of the full capital grant and proper central government funding for the Tube.”
A Transport for London (TfL) spokesperson said in response:
We are undertaking the largest ever overhaul of our organisation to provide the most efficient and cost effective transport service for Londoners. We have already reduced management layers and bureaucracy and merged functions in other areas to eliminate duplication and reliance on expensive agency staff.
We do not recognise the RMT’s number. Over the next few months we will be consulting on further plans in a number of other managerial, support and other non-frontline areas across TfL and London Underground. None of this will compromise safety, which will always remain our top priority.
Last December, TfL unveiled a five-year business plan, involving trimming jobs to save £800m a year. London mayor Sadiq Khan said "a flabby TfL" needed to shape up, through cutting management layers and curbing spending on consultancy and non-permanent labour.
It comes as TfL looks as to how it can cover all its operating costs from fare and non-fare income, as the central government revenue grant is phased out.
The 2017/18 year will be the last the transport body will receive a general grant from the Department for Transport, which helps account for its operating costs.
In TfL's annual report for 2016/17, it said progress had been made, with day-to-day operating costs of running the network decreasing for the first time since TfL began operating, by £153m, but acknowledged "this focus will need to be sustained in the coming years".
Gareth Bacon, Conservative group leader on the London Assembly, said today that part of the blame over prospective job cuts rested with the mayor.
“Sadiq Khan will more than likely blame the government, he should instead accept the consequences of his own actions," he said. "He urgently needs to U-turn on his unaffordable pledge to freeze TfL fares, and Hopper bus tickets which have cost more than three times TfL estimates."
Bacon added: "There are sensible savings that Sadiq Khan is ignoring like stopping the gold-plating of TfL pensions, standing up to militant transport unions and fast-tracking the move to driverless trains."