Victoria has declared a code brown emergency for all its Melbourne hospitals and six in the regions, as the system buckles under COVID-19 admissions and staff shortages.
Acting Health Minister James Merlino announced the measure will come into effect from midday on Wednesday and last for four to six weeks as hospitalisations are expected to peak.
The order means each hospital will be able to postpone or defer care that is not urgent, while some staff may be reassigned or recalled from leave.
Staff will only be recalled from leave if "absolutely necessary".
Mr Merlino said the state's hospital system is under "extreme pressure" from staff shortages. More than 4000 healthcare workers are isolating having either tested positive for the virus or as close contacts of a positive case.
"We've reached a point in our health system where it's juggling severe workforce shortages, we've got more than 4000 health care workers unavailable right now, alongside a vast number of patients with COVID-19 who require hospitalisation," he told reporters on Tuesday.
"We've always known that this would be the case, that as we move away from lockdowns and remote learning there will be a strain on our hospital system and we are seeing that play out with significant numbers via the Omicron wave.
"This is all happening alongside the continued need to treat patients with urgent and emergency needs."
Mr Merlino said hospitalisations in NSW, where the Omicron outbreak is a couple of weeks ahead of Victoria, continue to increase by about 100 people per day.
"If we see what we've been seeing in NSW, we could well get to over 2500 hospitalisations and more over the next few weeks so now is the right time to implement this plan," he said.
The code brown applies to all metropolitan Melbourne public hospitals as well as the regional Barwon Health, Grampians Health, Bendigo Health, Goulburn Valley Health, Albury Wodonga Health and Latrobe Regional Hospital.
It is the first time the Victorian health system is having a system-wide code brown. They are usually reserved for short term emergencies, such as the Black Saturday bushfires and deadly 2016 thunderstorm asthma event.
Victoria recorded 20,180 cases and 22 deaths on Tuesday, with 1152 patients in hospital.
The new infections confirmed by the health department include 11,747 from rapid antigen tests and 8433 from PCR tests.
It is the second consecutive day case numbers have declined in the state.
It brings the total number of active cases to 235,035 - a fall of about 10,000 cases since Monday.
Tuesday's patient numbers are a decrease of 77 on the previous day.
The number of people in ICU has decreased by two to 127, though 43 people are now on ventilation, an increase of five.
