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.
Unite regional officer Terry Cunliffe called for talks to avert the action, adding: "This is a final window of opportunity for the trust to resolve this situation for the benefit of the Yorkshire public.
"The management has been trying to silence Unite after it raised legitimate concerns over patient safety that could flow from the shake-up of ambulance services in the next five years.
"Now our members have voted for strike action and for a continuous overtime ban. It shows the depth of concern that our members feel about patient safety because of the £46 million of savings that managers want to implement.
"The hardline management has responded by derecognising Unite and twice rejecting our attempts to take this dispute to Acas and to discuss the implications of industrial action."
Stephen Moir, Deputy Chief Executive at Yorkshire Ambulance Service NHS Trust, said: "We would like to reassure members of the public that the changes we are introducing to our A&E workforce will enable us to continue to deliver a high quality and responsive service to patients and they will always remain our top priority.
"We would also like to provide assurance that the Trust has plans in place to avoid any disruption to patient care if Unite union members decide to go ahead with the industrial action they have outlined today."