Drivers on London Underground's Jubilee Line plan to hold two strikes in June in a row about new timetables.
Members of the Rail, Maritime and Transport (RMT) and Aslef unions will walk out for 24 hours on 6 and 14 June.
RMT General Secretary Mick Cash said the new timetables "ride roughshod" over rostering agreements and said drivers were "angry at the impact on work-life balance".
Transport for London (TfL) said the timetable "will benefit thousands".
Aslef official Finn Brennan said the the new rosters increased the number of Saturdays drivers have to work, breaking a previous arrangement made during a 2015/16 pay agreement.
"Despite the rhetoric from City Hall about wanting to work with trade unions to avoid conflict, senior management... have ignored every offer to sit down and discuss this issue," he said.
Mr Cash accused managers of being "out of control and hell-bent on imposing change through diktat rather than through the established negotiating machinery."
Nigel Holness, London Underground's director of network operations, said the changes would extend peak-time service from 30 minutes to two hours and could be implemented within current rostering agreements.
"We encourage the unions to continue working with us... rather than calling for unnecessary industrial action," he said.
A strike on sections of the District Line is also due to be held by Aslef members on the same dates as part of a separate dispute.