Delegates to the Yorkshire and Humber TUC conference threw their weight behind the Yorkshire Ambulance Service staff at the weekend.
Yorkshire Ambulance Service Trust derecognised Unite last month after the union publicly voiced concerns over the trust's plans to downgrade ambulance staff, putting patients' lives at risk.
Paramedic Debbie Wilkinson said she had never been more worried for the ambulance service.
Instead of ambulances being staffed by paramedics qualified to degree level, the trust plans to replace hundreds of paramedics with "ambulance assistants" receiving just six weeks' training and much less pay.
Unison member John Cafferty said if the trust succeeded it would send a message to employers across the country to simply derecognise unions whenever bossed faced opposition from unions.