Health Minister David Clark has refused to be drawn on whether district health boards (DHBs) are underfunded, but conceded they are under pressure.
Dr Clark told TVNZ1's Q+A he did not accept financial deficits are inevitable.
"Some DHBs are returning small surpluses. Some break even. Some return small deficits," he said.
Dr Clark's comments come after DHB deficits increased $40 million in May.
"It's been stretched for a long time... $2.3 billion more would need to have been put in just to maintain the same level of services. You can't fix that in one or two budgets."
"If we put a whole lot more money in right now, there wouldn’t be the workforce to deliver on all of our aspirations. There’s no doubt that we want to grow and strengthen the public health service.
"I want to put more money in. We pledged $8 billion in Opposition; actually, already in two budgets, we’re well over halfway there, and we’re going to keep putting more money in."
But National say that is not good enough.
"Labour is failing to deliver on its promises," Opposition leader Simon Bridges said. "David Clark and Jacinda Ardern in Opposition made quite clear they would deal with deficits - well they're ballooning."
Mr Bridges said "this is because they put money into a bunch of other things... and they're not prioritising our health".
"I think it's a really serious issue, I don't know if it's necessarily about significant overhaul as much as it is following through on your promises."
Mr Bridges said if in Government, National would have made "sure we were funding health right" and would bring back targets in the health sector.
Dr David Clark also said he was open to the idea of a smaller number of DHBs.
"Some of the DHB's are already sharing resources across different areas and it seems to make sense; they’re doing it organically," he said.
The Health Minister defended the Government's drug buying agency Pharmac on Q+A, saying to expect more funding to go into the model.
"Last year 331,000 patients benefited from access to more medicines through either broadening access to some existing medicines or through the 13 new medicines that were approved last year," he said.
When challenged that Pharmac funding wasn't keeping up with inflation, Dr Clark said: "The Pharmac model delivers more medicines to more people every year... it actually has that ability to apply at scale and negotiate".
Q+A is on TVNZ1 Mondays at 9.30pm, and the episode is then available on TVNZ OnDemand and as a podcast in all the usual places.