It comes after the RMT union has announced a fresh Tube strike that is expected to cause major disruption across the London Underground on the same day.
Now Unite members at TfL and London Underground have said they are taking action in a row over pay, pensions and jobs.
More than 1,000 Unite members have said they will walk out in protest at plans to cut the value of their workers’ pensions and close the existing final salary scheme.
The capital’s underground could be affected again on June 22 due to a separate row over shift patterns.
Unite general secretary Sharon Graham said: “It is not acceptable in any way, shape or form that the dedicated workers at TfL and London Underground are being told to pay the price of the pandemic with their pensions, pay cuts and threats to their jobs.
“Unite’s members have their union’s total support. These unwarranted threats to our members’ retirement savings, pay and jobs must be taken off the table at once or strike action will hit the London’s transport network.”
They have warned it will cause severe disruption across London.
Unite regional officer Simon McCartney said:“Strike action will inevitably cause severe disruption across London but this is a direct result of TfL management’s repeated failure to offer guarantees on pensions, pay or job cuts.
“Strike action and the resulting disruption can be avoided by TfL making a clear commitment it won’t cut workers’ pensions or jobs, while also making a cost of living pay rise to our members.”
The Standard has approached TfL for further comment.
More to follow