Private hospital elective surgery is growing at triple the rate of public surgery, the agency responsible for monitoring Australia's health system has found.

Experts say patients desperate for surgeries such as knee reconstructions and cataract removal are flocking from poorly resourced public hospitals. They also fear Australia is developing a two-tier health system, where people who can afford private healthcare are treated more quickly, often by publicly-funded doctors working in the private system.

Two Australian Institute of Health and Welfare reports released on Tuesday show there are now more than double the number of elective surgery procedures performed in private hospitals than public.

Institute spokesman Nigel Harding said two-thirds of elective surgery was now performed privately, and there had been faster growth of the private system over the past five years.

"A lot of the growth has been in elective surgery and day surgery," he said.

Catholic Health Australia chief executive officer Martin Laverty said the figures showed the continued capacity constraints faced by public hospitals.

"It makes sense that we are finally using private hospitals for delivery of elective surgery … which the Productivity Commission has found [in some cases] costs less than in the public system," he said.

But he cautioned that more needed to be done to properly plan where private hospitals could be most effective, and ensure people who could not afford to pay did not have to wait too long or miss out.

"In the UK and France you can see a much greater willingness of governments to use private hospital beds to treat patients regardless of whether they are public or private," he said.

The Institute’s reports show that about 4 per cent of private hospital funding comes from state and territory governments.

Jeff Richardson, foundation director of the Centre for Health Economics at Monash University, said the figures significantly underplayed the amount of funding for private hospitals because many doctors were paid for by Medicare.

The Institute's reports show salaried doctors are about 2 per cent of the staff at private hospitals, compared to 13 per cent of the staff at public hospitals.

Professor Richardson said Australia had one of the "least egalitarian" systems in the world.

He said that while having elective surgery in the private system took away the patient burden, it also took the doctors, and research indicated some private hospitals used more resources than public hospitals.

"The private system drives resources, both financial and medical, away from the public system," he said. "Both political parties have endorsed a two-tiered system."

Consumers Health Forum spokesman Mark Metherell said the widening gap in access to elective surgery between private and public patients underlined the emergence of a two-class health system, rather than reduced strain on the public system.

"The majority of Australians who do not have insurance suffer, and waiting times for elective surgery in public hospitals continue to lengthen," he said.

The Institute’s reports show that while the number of public hospital beds has increased in NSW, this has not kept pace with the growing population, meaning the number of beds per per person has dropped. Across Australia there are fewer beds per person than the Organisation for Economic Co-operation and Development average.

They also show that the number of beds available for people with mental illness has decreased, as has mental illness outpatient treatment.