Members of the Rail, Maritime and Transport union will strike on Friday 19 August as part of their long-running fight for jobs and pensions.
The news comes ahead of a 24-hour strike by the RMT this Wednesday, which will see tens of thousands of Network Rail workers and 14 train operators walk off the job.
The Transport Salaried Staff Association (TSSA) has also announced a strike by its members at Avanti West Coast on Wednesday, while members of the eight-company Aslef drivers’ union will strike on Saturday.
The RMT union has announced two more days of rail strike for August 18 and 20.
The union said the new London Underground strike had been prompted by Transport for London’s refusal to share details of a draft government proposal they received regarding funding for the capital’s transport system.
Read more: Wednesday’s rail strike: What to know as industrial action continues
RMT general secretary Mick Lynch said: “Our members will be picketing again in this important dispute over pensions, jobs and conditions.
More information about the London Underground
“They’ve been screwed by TfL and Mayor Sadiq Khan. And to add insult to injury, they haven’t seen the detail of this government funding letter.
“Unless there are guarantees on jobs, pensions and damaging changes to working conditions, our strike on August 19 will go ahead.”
The union said it would give TfL until August 2 to give assurances on jobs, pensions and working conditions.