Doctors want the Health Ministry to stop demanding deficit cuts at Canterbury District Health Board, saying it cannot do so while the hospital is being rebuilt without cutting services.
Canterbury DHB recorded a deficit of almost $52m last financial year and expected the figure would be about $54m this year.
Documents released under the Official Information Act show the Ministry called for the deficit to be cut to $17m this year and for the board to return a surplus the year after.
That led the DHB to complain in July that savings on that scale would require it to make "significant service cuts of unprecedented scale".
Association of Salaried Medical Specialists head Ian Powell said pressures were already extreme in the Canterbury health system, and the Ministry needed to drop its demands.
"Unfortunately the Ministry is looking at this through a narrow lens, they're not seeing the wider context.
"We're already, in our view - from what I pick up from specialists in Christchurch - seeing pressures on the ability to provide safe accessible services.
"If the ministry pushes too hard, that situation will further deteriorate."
The DHB said the major Christchurch Hospital rebuild, the Kaikōura earthquakes, the cost of doctors' strikes and the region's rising population had ruled out being able to make savings.
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It refused to be interviewed but was in discussions with the Ministry.
The Ministry also refused to be interviewed, but said the DHB had received an extra $331m over the past eight years.
It also said it and the Treasury were willing to help, but that the board must move towards a financially sustainable future.
"This will require Canterbury District Health Board to find savings within its $1.4bn budget.
"Other DHBs have shown they can do this without cutting frontline services.
"DHBs have looked at rationalising back-office functions, curtailing international travel, reducing layers of managers, better staff management and reducing waste."
However, Mr Powell said what was needed now was for the Ministry to waive a contentious capital charge that would be imposed on the DHB because of the rebuild of Christchurch Hospital.
"Given the size of the natural disasters that Canterbury has been subjected to, in a way that no other DHB has been, there seems to me to be a compelling case to waive the capital charges given the extraordinary circumstances and limitations of the annual funding formula.
"In these circumstances, waive the charge."
That was backed by a Canterbury professor of general practice, Les Toop, who said the DHB was already more efficient than most other health boards, and could not be expected to make savings now.
"If you are investing in new services to save money elsewhere, if you cut them then in short order you will put unbearable strain on other parts of the system
"And then you start not meeting government targets and further upsetting the workforce.
He said the capital charge of 6 percent on the net value of the new hospital was like being kicked while you're down.
"The hospital is broken and you only get a chance to fix it out of the operating budget."
He said the funding battle needed to be sorted out, and the only way to do that was for the government to commission a truly independent review of DHB finances.