Now, Derrett says nothing has changed 11 years on except that access is worse and healthcare is almost a lottery depending on where patients live.
"We know things have not got better. We know that the rates of publicly-funded surgery has not been keeping pace with the increase in population.
"Access is much poorer for the poorest of the poor. In terms of equity this is a huge issue."
It follows a Supreme Court decision in Canada last month rejecting efforts to expand British Columbia's two-tiered medical system after Justice John Steeves preferred evidence that showed allowing more private healthcare would not free up resources in the public sector to reduce wait times.
Last month New Zealand experts said the decision cast a shadow over New Zealand's dual practice and called for a conversation about public versus private healthcare, in the lead-up and beyond the October 17 general election.
Derrett said she wanted to see action on the issue.
"We really need to be doing something dramatic like the UK where the National Health Service [NHS] was investing in increasing the amount of publicly-funded elective or planned surgeries."
There were other moves there to reduce the volume of backlog as well, she said.
"And New Zealand just hasn't seen that."
Derrett said the burden of the broken system fell largely on Māori and lower socio-economic groups.
"It's low-income New Zealanders. It's been like pulling teeth trying to get interest in this including from government."
In the Newshub leaders' debate last week Prime Minister Jacinda Ardern described the country's health system as broken.
But the two-year long national Health and Disability System Review, released in June and which found a fragmented system under serious stress the delivers unequal healthcare, did not explore the issue of public versus private.
Derrett said part of the problem was the mix of private healthcare drew educated voices away from the debate.
"If we start having the public system deteriorate to the extent that people like us feel there's no option but to have private insurance or pay for private treatment, what we're doing is we're exiting the public system.
"We're taking with us our well-educated, well-connected voices and our loyalty to the public system is then called into question."
If higher income New Zealanders paid for private healthcare there was a risk they won't bother campaigning for better service and access in the public system, she said.
"It's heartbreaking actually. We need cross-party agreement about fundamental levels of access to services for New Zealanders because what the current system is doing is turning a completely blind eye to the inequities that are going to fall most heavily on Māori and Pacific people and poorer New Zealanders.
"And since when have we in New Zealand been okay about a healthcare system that's that unfair?
"And why are we not seeing Government ministers carefully planning steps to address this?"
Both Health Minister Chris Hipkins and National's spokesman for health Dr Shane Reti have private health insurance.
Last month Reti told the Herald this was not a disincentive to improve the public system.
At the time 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.
"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."
Health commentator and former head of the senior doctors' union, Ian Powell, accepted there were inequities in New Zealand's health system but did not believe they were caused by private healthcare.
"Private healthcare does not impact on reducing public wait times because the demand in public is not so much from people who want to use private healthcare but people who can't."
