The Australian Nursing Federation (ANF) has backed nurses refusing to move to the Perth Children's Hospital until lead contamination has been sorted.

Head contractor, John Holland, says the water being delivered to the building is contaminated, but the WA Chief Public Health Officer disputes the claim.

Reports say up to 98 per cent of ANF members are refusing to work in the new hospital until the lead is removed.

“We'd like to have an independent third party test the water,” said ANF state secretary Mark Olson.

“They're not prepared to move over there to look after sick children. They know the risks associated with lead exposure, even minute amounts,” he told the ABC.

“We hoped that the Government would identify the source of the problem and told us all how they were going to fix it, that hasn't happened.

“Now it's getting to the stage where we don't want to see the Government announce some premature opening of this hospital until they have removed the problem of the lead.

“Not just filter it out to a safe level but to actually fix it and get a third party, not the people who have constructed the hospital, not someone from the Government but a third party to confirm that the lead has in fact been removed.”

Mr Olson said the WA Government was unclear about its plans.

Health Minister John Day says the Government is focused on the safe commissioning of the hospital.

“We will not open the hospital until we are absolutely certain that the water to be used by patients and staff meets Australian Drinking Water Guidelines,” Mr Day said.

“The hospital can and will only be opened after approval of the water supply by the independent regulator, the WA Chief Health Officer.”