Ambulance workers are to stage a 24-hour strike in a long-running row over issues including cuts.
Unite said its 450 members in the Yorkshire service, including paramedics and other staff, will walk out on 2 April and ban overtime from 26 March.
The union warned that further strikes could be held.
Unite said the Yorkshire Ambulance Service NHS Trust had derecognised the union after it raised concerns about patient safety over plans to make £46 million of savings over the next five years.
Union members voted by 61% in favour of strikes and 83% for other forms of industrial action.