The West Australian Government has confirmed it is paying $500,000 a month to a parking contractor to manage hundreds of unused parking bays at the delayed Perth Children's Hospital.

Health Minister John Day said the monthly fee was part of a contractual obligation for Capella Parking to manage 300 bays in an underground car park built at taxpayer expense.

Mr Day said the cost was unavoidable and flowed from a contract the Government signed with the parking operator about three years ago.

"I can understand why on first examination it seems a bit hard to defend, however it is part of a contract which has resulted in a $125 million car parking development which provides a lot more parking," he said.

"There is a cost in doing that. It has to be funded somehow by either taxpayers or by the Government from some other revenue source, or the private sector.

"The private sector naturally expects to have its costs covered and that's all that is happening."

He said the state was obliged to pay the operator to manage the bays, even though the delays in finishing and opening the Perth Children's Hospital meant the car park was yet to be handed over to Capella Parking.

"It was expected that the hospital would be open before now and that the car parking bays under the hospital would be in use, and therefore there would be some revenue from it," he said.

Government will attempt to recoup money

The $1.2 billion Perth Children's Hospital has suffered a series of delays, and still has no firm opening date with the contractor and Government yet to agree on how to remove or remediate asbestos roof panels wrongly installed in the building.

While the Government will continue to meet the cost of the parking contract, Mr Day said it would seek to recover the money from the building contractor.

"It's unfortunate that the hospital has been delayed ... and there will be negotiation with John Holland once the hospital is completed, about damages the state is likely to receive from John Holland because of the delay in the hospital opening," he said.

A spokesman for Mr Day said the hospital's basement car park was separate from the multi-storey development built by Capella Parking that has more than 3,000 bays and cost $120 million.

While the $500,000 compensation payment covers the entire parking contract, the spokesman said the clause was triggered by the delay opening the hospital and its basement car park.

Parking bill evidence of privatisation price tag: Labor

Opposition Leader Mark McGowan said the parking bill was reminiscent of the huge contractor fees paid for the delayed Fiona Stanley Hospital.

"A couple of years ago we were paying a fortune to Serco for a hospital without any patients. Now we are paying a fortune for a car park without any cars," Mr McGowan said.

Mr McGowan said it was further evidence of the high cost of the Government's push towards privatisation.

"The Liberal Party and their privatisation agenda is costing the taxpayers a king's ransom and the public, and in particular parents with children, are also going to pay through the nose when their car park starts operating."

Mr McGowan said the daily cost of car parking at the new Perth Children's Hospital was expected to be $23 a day, compared to the existing fees of 60 cents an hour at Princess Margaret Hospital.