Sir Charles Gairdner and Osborne Park hospitals will shed about 250 full-time jobs because health officials say staffing levels are unsustainable.
The Health Department confirmed yesterday that the positions would be scrapped, where possible through natural attrition and not renewing fixed-term contracts.
Ending months of speculation that 200 full-time equivalent positions could go from SCGH, North Metropolitan Health Service chief executive Shane Kelly maintained the cuts would not affect patient care.
Among the job losses are 67 in allied health areas including radiology, occupational therapy and physiotherapy.
"Patient activity at Sir Charles Gairdner Hospital and Osborne Park Hospital is not increasing at present and has been reasonably steady for the past couple of years," Dr Kelly said.
"As hospitals are now funded according to patient activity, current staffing levels, particularly at Sir Charles Gairdner Hospital, are not sustainable."
Dr Kelly said that both hospitals were already exercising stricter controls over staffing appointments.
The opening of new hospitals such as Fiona Stanley and Midland, and the projected growth in demand, meant there would still be significant demand for staff in the metropolitan area.
But Health Services Union WA secretary Dan Hill said the job losses would have a heavy impact on workers and patients.
"There will be a huge impact on therapy for inpatient and outpatient services," he said.
"It hasn't been fully detailed to us yet but we're reliably informed that up to 30 FTE positions are going in occupational therapy and 20 in physiotherapy.
"There are lots of part-time staff so these cuts affect a lot more people than FTE numbers would imply."
Mr Hill blamed the cuts on the Government trying to make up for the budget black hole and the botched transition to Fiona Stanley Hospital.
Australian Medical Association WA vice-president Michael Gannon said the job losses would gut allied health services and delay patient recovery.
"There is no doubt clinical care will be compromised, and we'll end up paying for it in the longer term through increased length of stay and people who bounce back to hospital," he said.