Paramedics in the North West are being balloted for strike action in a long-running pay dispute.
GMB, the union for ambulance staff, said workers at North West Ambulance Service (NWAS) had waited for more than 12 years for the outcome of job re-evaluation.
The ballot is already open and will close on Thursday.
GMB organiser Mike Buoey said: “Our members have been astonishingly patient in waiting for their job to be re-evaluated for the years between 2005 to 2016.
“When this was finally completed two years ago, we re-entered into discussions with NWAS in good faith, but they are refusing to budge.
“After almost 13 years, our members are now saying enough is enough.”
Michael Forrest, director of organisational development for NWAS, said: “The evaluation of the paramedic role is arranged by an external body on behalf of the trust and our trade unions.
“We are disappointed that GMB has chosen to take this action whilst a process is still ongoing.
“Due to the complexity of the process, there have been some delays whilst clarification has been sought by both sides.
“The trust is committed to resolving the matter in partnership with all our trade unions. Talks are currently taking place and will continue until a resolution has been agreed.”