WA doctors want the new children's hospital to be reconfigured for more beds, arguing too much space has been set aside for offices and not enough for sick children.
Australian Medical Association WA president Michael Gannon said that after viewing internal plans, there were fresh concerns the space allocated to wards in the nine-storey Perth Children's Hospital was relatively small.
He remained critical of the State Government's decision not to build two extra floors but said "that boat had sailed" and the next best option was to maximise bed numbers within the planned structure due to open late next year with 298 beds.
The call was backed by Telethon Adventurers co-founder Rick Parish, who also campaigned for the extra floors and whose son Elliot was treated for brain cancer at Princess Margaret Hospital until his death in 2011.
Mr Parish said the current PMH cancer unit was routinely overcrowded and the new hospital would only accommodate two more cancer beds.
"There is absolute scope for looking for more space in the hospital but it's a matter of how we do that," he said.
Hospital plans show wards located at the ends of five levels, covering specialties such as burns, oncology, general medical, intensive care, adolescents and mental health, while the Telethon Kids Institute occupies space on levels six and seven.
Dr Gannon said that despite the overall size of the hospital, ward space seemed very limited, while large areas were designated for administration and other uses.
"This is the unfortunate inevitability of the Government's failure to build the two extra floors needed, and while we recognise that boat has sailed now, we need to deal with the reality of the superstructure they've built," he said. "And when you look at the plans, the administration part seems to take up a hell of a lot of space.
"In our view it is inevitable that in three to five years time, no matter what the promises of expansion of services out to Rockingham, Midland and Joondalup, they will need more beds in the children's hospital."
The Government claims there will be enough beds by the time all 404 paediatric beds open at the new children's hospital and other hospitals such as Fiona Stanley and Midland.
A spokeswoman for the Child and Adolescent Health Service said the children's hospital could be expanded later if needed.
Up to four extra floors could be added to the centre core block of the hospital, causing minimal disruption to normal hospital activities because it was not above inpatient areas.