Up to 1,400 job losses are planned at Transport for London because of spending cuts, the Rail, Maritime and Transport (RMT) union has said.
The union said that the roles include engineering and jobs on the London Underground.
The figure emerged at a meeting between union leaders and TfL on Tuesday, which the RMT said revealed that spending will be cut by £5.5 billion by 2021.
Mick Cash, RMT general secretary, said: “All the Tube and TfL unions have been sent written details of the next phase in the wrongly named transformation process.
“As part of the Mayor’s efforts to slash spending by £5.5 billion 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 LU.
“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 TfL spokesperson said in a statement: “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.”