Nurses at Fiona Stanley Hospital have threatened to walk off the job over further allegations of unsafe practices.

The Australian Nursing Federation (ANF) has raised concerns about essential surgical equipment going missing or not being properly sterilised.

State secretary Mark Olson said in many cases, the problems were only discovered mid-surgery while patients were on the operating table under anaesthetic.

In one example, nurses said they had to cobble together two different retractors to hold back a patient's abdominal wall during a liver operation because essential parts were missing from a surgery pack.

That came after blood and body tissue was found on medical instruments at the hospital.

The federation will hold a stop work meeting with nurses tomorrow to discuss taking industrial action.

Health Minister Kim Hames said services at the hospital had improved markedly since it opened in December, however, he conceded they were unhappy with this particular area.

He said Serco had been issued two breach-of-contract notices and has until Friday to respond to the second.

"If we need to, to protect patient safety, we will take action as soon as this Friday," he said.

Dr Hames said Health Department staff were also overseeing sterilisation procedures.

"We're told from staff that the service has improved considerably and remember our staff are there with oversight of the sterilisation process and the packing of the instruments and so on to make sure that we don't have any incidences like that again," he said.

"If Serco are not doing well enough in this particular area to satisfy us, then we need to change that and we will put our people in and run that service."

'Teething problems' downplaying situation: union

Last week Premier Colin Barnett described ongoing issues at the hospital as "teething problems" but Mr Olson said he was simply trying to downplay the problems.

"It's OK to have instruments regularly missing from theatre packs?" he said.

"It's OK to have bone fragments turning up in supposedly sterilised equipment?

"That's not teething problems; to be happening on a regular basis, that's not teething problems."

Mr Olson has called on Dr Hames to resign.

"That's evidence of a Health Minister clearly out of touch and showing no interest in his portfolio," he said.

"The Minister should've been sacked a long time ago."

Mr Olson said all surgery should be transferred to other hospitals until the State Government could ensure patient safety.

He said nurses had been raising the issues since the hospital opened and he was considering contacting Worksafe.

The union has also urged patients who have had surgery at Fiona Stanley Hospital in recent months to be tested for infection, however, Dr Hames said that was simply scaremongering.

"There is no reason to be alarmed and there is no reason to be concerned because no people that have had procedures have had them with contaminated instruments," he said.

The opposition's spokesman for health, Roger Cook, said the union's claims were alarming.

"I'd be very concerned if there's any hint of a possibility that people may contract diseases over the Barnett Government's failings over the privatisation of sterilisation services," he said.