St John Ambulance figures reveal ramping - where patients are forced to wait in ambulances for more than 30 minutes before being handed over to emergency departments - increased across the metropolitan system to a record 3074 hours last month.

The previous high was 2746 hours in June 2019, during a record flu season.

Doctors are particularly concerned that the spike coincides with WA recording fewer flu cases because of precautions related to the COVID-19 pandemic.

"When we have people waiting four or five hours in waiting rooms, unable to be assessed, that is not optimal in any circumstance," Australian Medical Association emergency medicine spokesman Dave Mountain said on Thursday.

"That is a disaster for them, it's a disaster for the system and patients do die because of those changes in the system. If they cannot get to an appropriate bed at the appropriate time, we know that increases mortality rates."

Premier Mark McGowan on Thursday said there were more intensive requirements for cleaning ambulances because of COVID-19, which he said had "slowed everything down" across the system.

The claim was rejected by Dr Mountain.

"The definition for when you come off a ramp doesn't include the cleaning time so that makes no difference to the ramping time," he said.

Opposition health spokesman Zak Kirkup said the premier's claim was "absolute nonsense".

"As a volunteer ambulance officer I can tell you that cleaning down an ambulance and patient paperwork is not included in ramping statistics," he said.

"We need to better resource our health system and expand our emergency departments. Clearly, there aren't enough beds in our hospitals. Labor need to fix this now."

Mr McGowan defended his government's management of the health system.

"I just think the Liberal Party has gone into overdrive on negativity. They're trying to tear down everything we do to defeat COVID in Western Australia," he said.

"Nationally our emergency departments and our hospitals are the best in the country."

Australian Associated Press