Consultant renal physician Dr Gavin Carney was a visiting medical officer (VMO) at the hospital from 1998 managing about 40 per cent of its dialysis and kidney transplant patients until November 1 when his contract ended.

He was one of three private specialists told earlier this year their contracts would not be renewed and he says ACT Health gave him no explanation.

Apart from a small 3.5 per cent spike in VMO numbers in 2013/14, when there were 198 doctors, up on 191 in 2012/13, the numbers of visiting specialists contracted by ACT Health each year since 2006-07 has grown at a slower rate than salaried specialists, figures provided to the ACT Assembly reveal.

The most stark contrast was in 2012-13 when VMO numbers fell by 5.8 per cent, from 202 to 191, while the numbers of salaried specialists increased by 7.8 per cent from 218 to 235.

ACT Visiting Medical Officers Association president Dr Peter Hughes said VMOs were being denied the opportunity to take up positions at the hospital, making Canberra "a black hole" that specialists were avoiding.

ACT Health's jobs website shows there are currently six vacancies for "senior" or "staff" specialists, only one specifically open to VMOs.

"We feel it's important to have the mix of visiting specialists, who are part-time in private practice, as well as salaried specialists," Dr Hughes said.

Dr Carney, who is also secretary of the VMO association, said his departure from the hospital was part of ACT Health's agenda to eliminate VMOs, who work as independent contractors, in favour of staff doctors who could be "manipulated" like public servants.

He said the policy was costing taxpayers more, with staff doctors expected to dedicate just one-third of their time to treating patients and the rest juggling administration, research and teaching.

"Everyone knows we are running out of money [for healthcare]," Dr Carney said.

"To give the service a fair go you must employ VMOs otherwise you run down the private sector, you de-skill people like me because I no longer have access to the public system and give it a few years and you won't have specialist physicians in the community."

Health Minister Katy Gallagher told the assembly staff specialists cost $181 an hour, while VMOs cost $238 as of July 2013.

But Dr Carney said comparing hourly rates did not take into account the expenses VMOs covered themselves, such as secretaries and superannuation, which for staff doctors were paid by the government.

"When you properly cost these [staff specialist] doctors they are the most expensive doctors in the world," he said.

A spokeswoman for ACT Health would not comment on individual VMO contracts, including Dr Carney's.

She denied there was a policy to reduce the numbers of VMOs, but admitted ACT Health was transitioning away from a "predominantly VMO workforce" to become "more balanced" as the tertiary hospital had growing requirements for teaching, training and research as well as clinical practice.

"Salaried specialist positions require doctors, as part of their employment, to be involved in more than just clinical service provision," she said.

She said VMOs did do teaching, training and research, but their focus was on clinical services.

Dr Carney said his 90 transplant and 60 dialysis patients from Canberra and NSW were under pressure to change doctor, since his contract had ended, unless they switched to private healthcare which many could not afford.

"If you had been seeing a doctor for 20 or 30 years, do you want to be told by some administrator 'bugger off and see another doctor'?" he said.

"They're treating them like a herd of cattle.

"I still see the same patients and I write letters to the hospital, but I'm in a position where I can only advise [hospital staff], I can no longer direct."

Although Dr Carney was given the opportunity to reapply for his position as a salaried specialist, he said the selection criteria was deliberately created to exclude physicians such as himself who did not have recent research experience.