Hundreds of ambulance staff have threatened to strike after today's vote backed industrial action.
The action, which would include paramedics, drivers and control room staff, is centred on a pay dispute.
Union Unison said 97 per cent of those who responded to an indicative ballot voted in favour.
Branch secretary Gillian Humphreys accused Northern Ireland Ambulance Service bosses of deciding on pay bands before consultation on the impact of the Department of Health's Agenda for Change was complete.
The Agenda aimed to increase the pay of a million NHS workers by about 10 per cent over three years.
Ms Humphreys said the policy gave staff rights of equal pay for equal value jobs and claimed this was being overridden by managers.
"It has taken 18 months to come to this point but we have to draw the line somewhere and the fact is that only 2.8 per cent of those who responded were against this," she added.
"The vast majority of ambulance staff have voted for industrial action up to and including strike action."
She will now initiate legal proceedings to allow a formal ballot which would give the go-ahead for strikers.