A Supreme Court decision in Canada rejecting efforts to expand British Columbia's two-tiered medical system casts a shadow over New Zealand's dual practice, doctors here say.
Together with experts they are calling for a conversation about public versus private healthcare, in the lead-up to October's election.
The 880-page judgment by Justice John Steeves, released last week, found that provincial laws putting limits on private practice did not contravene the Canadian Charter of Rights and Freedoms.
While some patients experienced increased suffering over long wait times for surgery and procedures, Steeves was not convinced the expansion of the two-tiered system would free up stretched resources to improve this situation.
Instead he said there was a strong connection between the duplicative private healthcare and increases in wait times in the public system.
Dunedin Hospital consultant surgeon and intensivist Dr Mike Hunter said most New Zealanders would believe that making private alternatives available increased people's access to medical care and took pressure off the public system.
"But the judge took a contrary view to that. He accepted that actually it degrades access in the public system and it produces a distortion of care available to those with the ability to pay but makes it worse for those who don't have that ability.
"I think he's right. I think though, the history and culture and familiarity with the dual system would make it very hard to make any progress on this politically in New Zealand."
Hunter said people viewed private healthcare as a fundamental freedom, being able to opt out such as they do with schooling.
"I think philosophically and ethically the judgment has a great deal of merit and I think it's a conversation we should have, but I would be very surprised if there's an appetite for that sort of change."
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He urged New Zealanders to read the judgment, the culmination of a four-year trial including more than 100 witnesses, and question whether they would want more taxes funnelled into public healthcare.
One of those expert witnesses, New Zealander Dr Jacqueline Cumming - an independent health policy consultant - agreed a discussion about private healthcare was needed.
"What is the impact of having private health insurance and are New Zealanders happy for the current approach or do they think there might be reasons for doing exactly what the Canadians have done?"
She said equity and workforce shortages were big concerns under New Zealand's current system.
"New Zealand health survey data clearly shows that it's the wealthier people who have private health insurance and lower income people don't and that means that you can actually access faster services because of your ability to pay.
"It's actually really difficult to prove that if you do allow people to work in a private sector exactly what the impact is but it's certainly possible the impact could be that there's fewer hours available for the specialist to work in the public sector.
"And that in turn then impacts on the ability of the public sector to provide all the services that they are paid for and that could then blow out waiting times to be longer than they otherwise would be."
Gynaecologist Dr Alison Barrett said in an essay on the subject New Zealand's private healthcare system harmed the public system.
She said tolerance of the two-tier system exacerbated resourcing problems because doctors were "moonlighting", there was administration duplication and patients with means were able to queue-jump.
Moonlighting allowed doctors working in the private system to benefit from the dysfunction of the public system, Barrett said.
"The same doctor with a foot in both camps, can put a patient on a public waiting list where they will wait for a long time for a potentially less experienced person such as a registrar who is not fully trained to perform their procedure.
"Such doctors can tell the patient they could have their procedure done by a specialist consultant (themselves) on the day of their choice in the private hospital."
The conflict of interest is unique to doctors, where those competing in private who stand to make substantial profit are in a position of control of the delivery of public services.
Barrett said modelling of the scenario predicted that moonlighting physicians decreased their quality of care in the public system in the absence of penalty for low quality healthcare.
This led to dedicated doctors lowering their efforts in the public sector, of which Barrett said there was real-world evidence.
A Canadian study found ophthalmologists who performed cataract surgery in both public and private had waiting times of 15 to 20 weeks where surgeons who operated in public only had wait times of seven to eight weeks.
She said the public system propped up the private system with doctors who train in New Zealand doing so at substantial taxpayer cost.
Skimming, where doctors took easy work and left difficult procedures and complex, sicker patients to the public system, also caused problems.
"Proponents of private medical care argue that, should the private system stop functioning, the public system would be overwhelmed by the extra workload.
"But the financial incentives in private practice lean toward unnecessary procedures, and some of this extra workload is generated by these market forces.
"The complications from these procedures are often flicked back to the public system, which cleans up the mess.
"Perhaps if there was no such thing as a two-tier system, and our elected representatives had to subject themselves to the same public system as everyone else, they might work harder to fix it."
A former deputy director general in the Ministry of Health, Kathy Spencer, said the British Columbia model guaranteed access to medical care was based on need and not ability to pay.
She said the fairness of New Zealand's two-tiered system and the impact it has on those who miss out, was rarely questioned.
Spencer said based on Ministry of Health data for September last year, none of the country's 20 district health boards was meeting waiting time targets for surgeries such as hip, knee or heart valve replacements, a cardiac bypass or major back surgery.
"And the targets aren't what I would call ambitious; specialist assessments are meant to happen within four months of referral by a GP, and actual operations should happen within four months after that. Eight months in total is far too long to be waiting."
Spencer said a national review of health, led by Heather Simpson, did not include any recommendations to reduce long waits, and the role of private health insurance was excluded from the terms of reference.
"This shows how little priority and attention is being given to the inequities of our current two-tiered system."
Both Health Minister Chris Hipkins and National health spokesman Dr Shane Reti have private health insurance.
Reti said this was not a disincentive to improve the public system.
"A key priority for me is developing the capacity of the public health system. I want the skills, equipment and policies across the public health system, not just public health, to lift up."
Reti believed the Canadian system was "confused and increasingly seen as underperforming", and that there was a place for private healthcare.
Hipkins said his health insurance was part of a life insurance package he obtained some time before becoming an MP, and had no bearing on his commitment to improving public health services.
He said countries with strong public health systems produced better outcomes and his priority was to build such a public health service.
"Where there are capacity constraints in the public health service, I am not opposed to the use of private providers to help speed up treatment.
"In the long term, however, I expect to see improved capacity in the public health service as we address the legacy of underfunding from the previous government.
"This will take time but we are making progress in our work with DHBs to build capacity."