Nurses at Adelaide's largest hospital will refuse to admit new patients to an acute mental health ward, citing safety concerns.
The Australian Nursing and Midwifery Federation (ANMF) says the Royal Adelaide Hospital's Ward C3 is unsuitable for vulnerable patients.
They've called for the re-opening of a five-bed psychiatric extended care unit which ANMF SA chief Elizabeth Dabars claims is currently sitting empty.
Prof Dabars says nurses on Ward C3 are unable to keep patients in their sights and are concerned about the presence of ligature points.
"There's been at least three very recent critical incidents where the outcome could have been a fatality," she told AAP on Friday.
"Fortunately that hasn't happened but people are just so concerned that they've said enough is enough."
Prof Dabars said she had been told mental health patients were continuing to be kept for extended periods in the Royal Adelaide Hospital's emergency department.
The union had been told the extended care unit would not be reopened unless the number of mental health patients exceeded capacity, she said.
Central Adelaide Local Health Network chief Julia Squire said in a statement on Friday she was working closely with the ANMF to address its concerns.
"A full response has been provided to the ANMF, which includes the allocation of additional nursing and security staff to the Royal Adelaide Hospital mental health facilities," Ms Squire said.
