The interim report of the review, commissioned by Labor while in opposition and released on Wednesday, found 1436 of 13,981 usable inpatient beds were not being used.

More than one fifth of beds at Barwon Health were vacant earlier this year, as were 19 per cent of capacity at Eastern Health and 13 per cent at Western Health.

At the Royal Children's Hospital, which has the longest waiting list in the state for elective surgery, about 13 per cent of beds were unused.

Australian Nursing and Midwifery Federation Victoria's assistant branch secretary Paul Gilbert said many unused beds appeared to be in metropolitan hospitals where there would be demand.

"They are going inactive due to the amount that is not being spent in health," he said.

"Waiting lists are getting longer and hospitals aren't using those beds as they don't have sufficient funding to do so."

Premier Daniel Andrews said the beds could be used if health was better funded, but improvements could not come at the "flick of a switch".

"This is a big job, a very big repair job, one that's going to take some time, and I'm very conscious not to be overpromising the Victorian community," he said.

He said it was important to consider the workforce needed to look after additional patients, whether building works were needed, whether the unused capacity was in areas of demand and federal funding pressures.

Mr Andrews pledged $200 million towards a hospital "rescue fund" last November to open up more beds.

The review was carried out by former Australian Medical Association Victoria president Doug Travis, who surveyed the state's 86 public services for the report. He looked at all "points of care", which include not just beds but also trolleys, chairs and cots.

Dr Travis said a statewide health plan was needed to improve the balance between the capacity of the hospital system, demand for services and the existing use of resources.

"That is a mammoth undertaking and will take a few years," he said.

Among 15 recommendations in the review, Dr Travis urged more detailed reporting on the average time to clear waiting lists, and the time it takes to see specialists to be referred for surgery.

AMA Victoria spokesman Michael Levick said outpatient referrals were a "hidden waiting list" that obscured the true number of people waiting for surgery.

Commissioned last August, the review found 53 of the state's 290 operating theatres and 90 of Victoria's 1284 emergency department places were not being used.

It also found patients who would otherwise occupy 900 beds were receiving home based care.

Health Minister Jill Hennessy said the report was "the most extensive review of health services capacity" the state had ever seen.

"The previous Liberal government promised to open 800 beds. They broke that promise. They cut $1 billion from our health system. We are looking down the barrel of Tony Abbott cutting $13 billion from our health system," she said.

But Opposition health spokeswoman Mary Wooldridge said the Andrews government had yet to make a commitment on how it would open up more beds.

"Daniel Andrews needs to change from just criticising what happened in the past to articulating his plan for health into the future," she said.

The Travis review's final report will be presented to the minister later this year, and will include recommendations on how the government could best deploy the promised $200 million.