London Underground staff are to stage three 24-hour strikes and other industrial action over pay and night Tubes, the RMT union has announced.
The strikes will start on the evenings of 26 January, 15 February and 17 February.
Aslef and Unite union members have also confirmed they will take part.
RMT General Secretary Mick Cash said his union members were “furious” at the “bodged” introduction of Night Tube plans.
London Underground has offered a four-year pay deal over the issue and said it would hire part-time drivers to staff an all-night service at weekends.