More than 10,000 London Underground workers will be re-balloted for strike action in a long-running dispute over jobs and pensions, the RMT announced on Tuesday.
The tube union has been locked in a row with Transport for London and the Mayor for nearly a year, resulting in misery for commuters.
The RMT has now threatened more industrial action over plans to cut 600 jobs stations, with more roles across train operations and maintenance to follow.
Proposals have also raised the prospect of tube workers losing over 30 per cent of their pensions, the union said.
RMT general secretary Mick Lynch said: “Our members have taken several days of strike action over this last year and remain as determined as ever to get a just settlement on jobs, pensions and their working conditions.“
“The Mayor is under pressure from central government, but he must join us in resisting them and refuse to allow ideologically motivated financial constraints to be used as an excuse to attack tube workers.
“TfL has healthy revenue streams and our members are among the thousands of tube staff that make it a successful transport provider.”
“This re-ballot is vital to maintain the pressure on TfL and I urge all our members to vote yes in the postal ballot.”
The ballot will run until the May 23 and the current mandate runs out in June.
TfL Chief Operating Officer Glynn Barton said: "We have been notified that the RMT union will be re-balloting their members over the renewal of their mandate for industrial action over jobs, pensions and conditions.
"This is despite the fact that no proposals have been tabled on pensions following a Government mandated review into the TfL pension scheme. If any proposal is made in the future, this would require appropriate consultation and extensive further work.
“We urge the RMT to work with us constructively and not threaten London with further industrial action."
