Commuters are facing more disruption, as two strikes are being planned in early March which will affect the entire Tube network.
The dispute is over jobs, pensions and working conditions.
The union says more than 10,000 members working on the Tube were invited to take part in a ballot.
Of those who responded 94% voted in favour of strike action, the RMT said.
Although it is understood that this is less than half of all union members working for London Underground.
What is RMT saying?
RMT General Secretary Mick Lynch said: “Our members will be taking strike action next month because a financial crisis at LUL has been deliberately engineered by the Government to drive a cuts’ agenda which would savage jobs, services, safety and threaten their working conditions and pensions.
“These are the very same transport staff praised as heroes for carrying London through COVID for nearly two years, often at serious personal risk, who now have no option but to strike to defend their livelihoods.
“The politicians need to wake up to the fact that transport staff will not pay the price for this cynically engineered crisis.
“In addition to the strike action RMT is coordinating a campaign of resistance with colleagues from other unions impacted by this threat.
“The union remains available for talks aimed at resolving the dispute.”
What is TfL saying?
Andy Lord, TfL’s chief operating officer, said: “It is extremely disappointing that the RMT has today announced strike action, as no proposals have been tabled on pensions or terms and conditions, and nobody has or will lose their jobs as a result of the proposals we have set out.
“The devastating impact of the pandemic on TfL finances has made a programme of change urgently necessary and we need the RMT to work with us, rather than disrupting London’s recovery.
“We’re urging them to do the right thing for London, talk to us and call off this unnecessary action.”
Night Tube Strikes
Night services on the London Overground will however run as planned between Highbury & Islington and New Cross Gate.