WA's health minister has dismissed as "scaremongering" claims that patients at Perth's new hospital have been operated on with contaminated equipment.

But Kim Hames has again admitted that Fiona Stanley Hospital has had problems with sterilisation, which is done by Serco, and says the state government is not satisfied with the private contractor's record for the service.

Australian Nurses Federation state secretary Mark Olsen said patients had been kept under anaesthetic for extended periods while nurses looked around for clean instruments.

Mr Olsen said patients who had undergone surgery should be tested for serious diseases, including HIV, because there was no guarantee that equipment was safe, saying management was playing "Russian roulette" with patients' lives.

"It's a small price to pay for peace of mind," Mr Olsen told reporters on Tuesday.

Asked about the union's claims patients should be tested, Dr Hames replied: "Well, that's just nonsense - they're scaremongering.

"There has been no risk to patients according to the advice I've received.

"There is no reason to be alarmed and no reason to be concerned."

But the minister said Serco had until Friday to respond to a breach-of-service notice issued in December.

Dr Hames said health department workers had been helping Serco since February after receiving complaints that equipment was not making it to operating theatres on time.

Opposition health spokesman Roger Cook said Dr Hames had given Serco too many chances and the sterilisation service should be removed from its contract.

Mr Olsen said nurses would consider industrial action if nothing was done about their concerns.

Members will hold a stop-work meeting at the hospital on Wednesday.

ALLEGED CONTAMINATION INCIDENTS AT FIONA STANLEY HOSPITAL
- Bone fragments found on a drill before it was used to fix a broken hand
- Patient's hand surgery was delayed for three hours because equipment used the previous day was not sterilised
- Heart surgery patient was kept under anaesthetic because equipment was missing sterile pieces
- Patient with a broken jaw kept under anaesthetic because staff were given the wrong equipment
- Sterilised pack labelled as being a light cable and camera was discovered to be a drill during surgery
- Kit to fix a patient's broken leg was missing a screwdriver
- Improvised equipment was used during liver surgery because a piece was missing from sterilised kit