The Australian Paramedics Association said its members had tipped-off the union about the shortfall at the Hamilton station, which usually has at least three vehicles operating on a night shift.

The association said it had been told by members that the staffing problem in Newcastle occurred when vehicles from Hamilton were sent to cover shortages at Kurri Kurri and Raymond Terrace.

According to the union, paramedics across the Hunter were sent a text message at 3pm seeking staff to take the 7pm shifts but they were unable to be filled.

"Our members are telling us that this is now a very regular occurrence, which poses a risk to community safety," APA NSW spokesperson and Hunter paramedic Brendan McIlveen said.

"Fewer ambulances means much longer response times and puts patients' lives at risk.

"This bodes poorly for the upcoming weekend and in particular Friday night which, if recent history has told us, is another very tricky night for [NSW Ambulance] management to resource appropriately."

A NSW Ambulance spokesperson said 15 of the usual 17 crews were on duty in Hunter Zones 1 and 2 on Wednesday night.

"As is standard practice, the sector notified off-duty staff of vacancies via a sector wide messaging system and offered overtime rates," the spokesperson said.

"Staff routinely take advantage of extra shifts on offer but on this particular evening, the shifts were unable to be filled."

Mr McIlveen said Hunter ambulance crews needed to be better-resourced so demand could be met "even during peak periods".

"APA NSW is calling on NSW Ambulance to urgently reassess its paramedic crewing levels in the Hunter, to ensure that the local community can have faith that when they call triple zero, that a paramedic crew will be dispatched and be at their front door quickly," he said.

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