Yorkshire ambulance workers said today that they will vote whether to strike after bosses derecognised their union.
Unite is in dispute with the Yorkshire Ambulance Service NHS Trust, which is planning to cut £46 million in spending over the next five years through lower wages and replacing fully qualified paramedics with cheaper staff.
The union said it will put lives at risk.
The trust worsened the dispute last week by derecognising Unite, despite a national agreement with the union.
Unite represents 450 paramedics and other ambulance staff employed by the trust. More are represented by Unison.
It said it would ballot for a strike or action short of a strike.
The result is due by the end of February.
Regional officer Terry Cunliffe said: "I can confirm that Unite has begun the legal process to hold an industrial action ballot over the trust's unilateral decision to derecognise Unite.
"The management is 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.
"The trust's behaviour is mind-boggling given last week's Francis report, which placed great emphasis on whistleblowing and 'a duty of candour.'
"Whatever the outcome of the ballot, our members will always put patient safety first."
The emergency care assistants being introduced by the trust receive only six weeks' training, while paramedics undergo a two-year degree course.
Unite says managers are deploying unqualified staff to deal with emergencies.
"Response to 999 calls is becoming a postcode lottery," it said.
"The sick and injured may receive attention from a fully trained paramedic crew but they could get a private ambulance containing unqualified staff."
The trust currently has over 300 staff who will be demoted and deskilled as a result of the plans. Unite said most of them will have little or no chance of further training for at least seven years.