High levels of sick-leave left Victoria down 50 ambulances overnight and in a dangerous position, the boss of the state's paramedics union says.
Victorian Ambulance Union Secretary Danny Hill said he had been told of a 69-year-old Melbourne man who died after waiting hours for an ambulance during the shortage on Saturday night into Sunday morning.
The number of available crews across the city dropped from 120 to 90, while regional Victoria was down 20 crews, he said.
Mr Hill said paramedics had to drive "massive distances" to reach sick patients and just one per cent of the ambulance fleet was available at a certain point.
"It's been several years since we've seen this amount of resources dropped, perhaps only during COVID," he told AAP.
He detailed a "sad and tragic" incident at Surrey Hills in Melbourne's east reported to him, where a man had died after waiting four hours for assistance.
Mr Hill said the man's neighbours heard him calling for help about 2am and called triple zero but they were unable to get into his house and reach him.
"They called triple zero but because there were no resources available. He waited four hours," Mr Hill said.
"When resources finally did become available and they did send an ambulance to the patient, they found the gentleman to be deceased."
Mr Hill has been told the man had been calling out "for some time".
"Even if he got a delayed response, a response within one or two hours, even though that's way too long, the situation could have been vastly different," he said.
"They've eventually turned up and found him to be deceased, which is just so incredibly sad because it is a life that, absolutely, it's a life that probably could have been saved."
He said the situation overnight may have been made worse if not for several dozen off-duty paramedics who took on extra shifts.
An Ambulance Victoria spokesman said the health system was extremely busy due to seasonal illness in its workforce and the broader community.
"We have as many crews on the road as possible and our priority will always be responding to the sickest and most time critical patients," he said.
"We use a dynamic operating model that relocates resources as necessary to minimise rostering impacts."
Ambulance Victoria said it would review the Surrey Hills case and keep the man's family updated as it progressed.
Victorian Minister Colin Brooks said the effects of the pandemic continued to flow on to the state's ambulance service.
"Our ambulance services are sometimes stretched and we can't determine when people are going to be genuinely sick," Mr Brooks told reporters on Sunday.
"But we're making the investments in our ambulances to make sure they continue to operate even under the stress."
The paramedic union has been locked in negotiations over its next enterprise agreement for months, with pay and conditions such as unreasonable overtime emerging as major sticking points.
In August, Ambulance Victoria's chief executive Jane Miller resigned after 18 months in the role a few weeks after the paramedic union passed a vote of no confidence in the executive board.
Former Emergency Management Commissioner Andrew Crisp is interim chief executive during the search for a permanent replacement and is currently on pre-booked leave.
Opposition health spokeswoman Georgie Crozier said the situation overnight was "extremely concerning".
"Victoria is at risk when you don't have an ambulance system that is meeting the needs of the Victorian community and that is occurring under the watch of the Labor government," she said.
"We need our paramedics to be supported, we need the Victorian community to be supported when they need emergency care."
