A re-elected Barnett Government would take a hard line on reforming the public sector and launch a push towards privatising more services to help restore the budget to surplus.

Key points: Treasurer says Liberals will limit spending and costs instead of waiting for GST reform

Treasurer says Liberals will limit spending and costs instead of waiting for GST reform Millions saved via private-public partnerships in health, corrective services, Nahan says

Millions saved via private-public partnerships in health, corrective services, Nahan says WA Labor says Liberals are "financial vandals" who cannot be trusted

A Treasury update last week showed the budget in deficit at least until the end of the decade, but Treasurer Mike Nahan told a business function in Perth the Liberals were "committed" to balancing the books if returned to office.

Dr Nahan told 200 business executives at a Chamber of Commerce and Industry function that the Government had made huge progress in restraining spending and wages since the end of the mining construction boom.

He said it had also saved WA taxpayers millions through highly efficient private-public partnerships in areas like health and corrective services.

Dr Nahan flagged that approach would be continued and expanded if the Barnett Government was returned to power.

"We are committed to doing what we need to do to push, to drive us back to surplus, irrespective of what happens on GST," he said.

The Barnett Government has long complained about WA's low share of GST revenue, but the latest Treasury update showed a sluggish turnaround in returns from the tax, largely due to an increase in iron ore royalties.

Rather than waiting for a fairer GST deal, Dr Nahan said he would focus on constraining spending and costs.

"Living within the conditions that we're confronted with, rigged as they are, we will have to continue to restrain the growth of expenditure, and that will include areas that are very, very difficult," he said.

One of those areas concerns prisons and the Department of Corrective Services, with Dr Nahan citing a Productivity Commission report showing WA had already lowered the per day cost of incarceration.

"And how did we do it? We built and contracted out to the private sector, something that the Labor Party has railed against every day in Parliament," he said.

"And I assure you in the future, when we have to build another prison, it will be a private sector prison at half the cost of the public sector."

More savings in hospitals: Nahan

The Treasurer said if re-elected, the Liberals would continue a similar approach with hospitals.

He said while the Perth Children's Hospital had experienced significant problems, hospitals built and operated under public-private partnerships continued to save taxpayers money.

"When we opened the Midland hospital, opened on budget and on time, not problems," he said.

"We expanded the Joondalup hospital ... opened up, expanded, on budget, on time during the biggest boom in our state's history."

Meanwhile, Dr Nahan said the Liberals would make more use of the private sector to drive down costs, but would do so in a way that was incremental, not sudden.

"We have to slowly, steadily push down the cost of delivering services. Not in a Kennett-level crash and burn, we didn't do that, we won't do that," he said.

WA Labor has characterised Dr Nahan and the Liberals as "financial vandals" who cannot be trusted to deliver on their promises.