NSW association president Chris Kastelan said Premier Gladys Berejiklian had announced the recruitment of an additional 700 paramedics over four years to improve ambulance response times, reduce paramedic fatigue and support safety.

"The Hunter area was to receive a proportionate amount of those," Mr Kastelan said. "The Belmont station got an extra 10 paramedics and an expanded roster, and in theory, that would provide more paramedics for that area. But ultimately, with these enhancements, management are using these extra paramedics - which were designed to build the roster into a larger contingent of paramedics at Belmont - to plug the gaps in rosters around the rest of the Hunter area.

"So we are finding that the enhancement of paramedic numbers is being negated."

Mr Kastelan said it meant the community was waiting longer for ambulances, and paramedics were travelling longer distances to get to them.

"Because the enhancements have been moved to other stations on a day-to-day basis," he said. "The other concern is that if they are getting moved away and they are working on a skeleton crew at Belmont, it means the paramedics are working longer hours, treating more people, and you are getting a fatigued workforce."

It comes as an Auditor-General's report revealed NSW Ambulance staff had the highest rates of overtime, sick leave and excessive annual leave of any NSW Health service in 2018-2019.

"We want to hold this government to account," he said. "They said the Belmont roster would be enhanced because it was needed in that area, and that's what we'd like to see. Let's not rob Peter to pay Paul."

A NSW Ambulance spokesperson said the union's claims were "incorrect", and that Belmont Ambulance station was running at "operational capacity".

The station had a roster consisting of two day crews, one afternoon crew and one night crew.

"This roster reduces fatigue for paramedics, allows better work life balance, and limits any additional taxpayer expense in overtime costs," she said.

Hunter New England had received an additional 17 paramedics in 2018/19, with a further 25 in 2019/20.

"As with any emergency service, NSW Ambulance experiences surges in demand but life-threatening injuries or illness will always be triaged as a priority. The closest available paramedics respond to patients in the event of an emergency.

"The NSW Government will invest more than $1 billion in NSW Ambulance in 2019-20 including $27.1 million to employ 221 paramedics and call centre staff - which is the second tranche of record 750 workforce announced last year - to improve response times, reduce paramedic fatigue and support safety."