Three 24-hour Tube strikes are set to take place between March and April after a “breakdown in industrial relations”.
Over 400 Piccadilly Line Tube drivers will stage protests on 23 March, 19 April and 21 April.
The Rail, Maritime and Transport (RMT) union is in dispute with Transport for London over “’Bullying, harassment and intimidation” of Tube workers.
An RMT spokesperson said that union members have decided to strike over concerns including the “ageing Piccadilly Line fleet” which have “left drivers in a vulnerable position”.
RMT general secretary Mick Cash said: “The wholesale abuse of procedures and agreements by management on the Piccadilly Line is rife and amounts to the development of a campaign of bullying, harassment and intimidation that the union will not allow to continue.”
Operations director Pat Hansberry said: “It is disappointing that the RMT is once again threatening unnecessary strike action without seeking to resolve these local issues with us first.”