Hundreds of surgeries, including procedures for cancer patients, have been cancelled as nurses and midwives across Western Australia strike over an ill-fated pay offer.

The industrial action comes as the Australian Nursing Federation (ANF) ignored a summons to appear before the Industrial Relations Commission (IRC) this morning over the dispute over pay and conditions.

Thousands of nurses and midwives rallied outside the front of state parliament, chanting "we're not going to take it anymore."

Wearing their work uniforms and holding signs demanding a five per cent pay rise, they loudly booed the government's claims they are putting patient safety at risk by striking.

The protesters then marched to the nearby government offices at Dumas House, loudly cheering and waving banners to the ministers and their staff above.

Union 'risking patient safety'

A full-page newspaper ad by the government warned "Western Australians will experience disruptions at public hospitals today due to unprecedented and unlawful industrial action by the nursing union.

But the union said no patient's safety would be put at risk.

Addressing a sea of nurses in blue uniforms from the front steps of parliament, ANF state secretary Janet Reah thanked those nurses and midwives who had stayed behind to form a skeleton staff so that the strike could go ahead.

She then labelled Premier Mark McGowan and Industrial Relations Minister, Bill Johnston, as "cowards" for ignoring invitations to speak at the rally.

But the crowd's loudest jeers were saved for Health Minister Amber-Jade Sanderson who had also declined the invitation because the strike action was "unlawful".

The ANF assured its members it would financially support all those taking part.

"In my 23 years with the ANF nurses and midwives have never gone on strike, the fact that you're here today shows how desperate the health system has become," ANF director of legal services Belinda Burke said.

"And we know this is why nurses and midwives are leaving and reducing their hours."

At the conclusion of the rally outside parliament the nurses and midwives marched to the government offices at Dumas House where they directed chants towards the Health Minister.

"Amber-Jade give us a raise!" the crowd yelled.

And before the event ended nurses and midwives were told to continue with bans on working double shifts and bans on accepting more patients than a ward's designated capacity.

Pay demand would cripple finances: Premier

Speaking in Collie, Premier Mark McGowan called on nurses to stay at work and accused the ANF of breaking the law.

"It's erratic and unlawful, and they're not behaving in good faith," he said.

The Premier said an offer made last week met most of the ANF's key demands and was agreed to in principle by union leadership before they 'backflipped'.

"So, I don't understand why this industrial action is taking place against the orders of the Industrial Relations Commission," he said.

Mr McGowan said a five per cent pay rise was unreasonable and the state's $6 billion surplus did not change that.

"It is not reasonable to ask for that, and the state can't do it," he said.

"We want to make sure we protect the state from the recession that's coming next year."

Asked if he took any responsibility for the dispute resulting in strike action or any responsibility for potential adverse patient outcomes Mark McGowan placed the blame on the ANF.

"In the negotiations the nurses' union said 'if you provide that we'll settle', we provided that," he said.

"Then they said, 'if you provide this additional allowance for some of the more senior nurses we'll settle', we provided that, then they didn't settle."

"This is what we're dealing with… it's not a rational way that the nurses' union is acting."

The Premier said hospitals were already feeling the impacts of the strike.

'Blood' on government's hands

Ms Reah told 6PR Radio the Health Minister had called her before 6:00am today and effectively guaranteed the strike would go ahead when she said there would be no change to the wages offer.

"She asked me to call off the strike, she said we were putting patients and the community at risk, which I deny," she said.

"She also said she wouldn't be speaking to the members today as we are engaging in 'unlawful strike action' which again I deny that charge."

Nurses and midwives are demanding at least a five per cent pay increase.

Asked whether the union would have 'blood on its hands' if patients died due to the nurses' strike Ms Reah said the "blood" would be on the "government's hands".

Ms Reah also confirmed she boycotted her summons to appear before the IRC this morning because she believed it was an attempt to prevent her from attending the 11:00am rally.

Lumpectomy delayed

Ms Reah claimed category one elective surgeries would still go ahead amid the strikes, but that wasn't the case for Sally-Anne Kelly, who was booked in for a breast cancer lumpectomy at Fremantle Hospital.

On Thursday, Ms Kelly attended hospital for a procedure that injects dye into the breast to prepare for a lumpectomy.

Ms Kelly described the procedure as "invasive" and the kind of thing you don't want to do twice, but as she left the hospital, her husband was contacted confirming her surgery the next day was cancelled.

It's what Ms Kelly expected would happen when she heard the news of the strikes, but she said they should have told her earlier.