Ousted health boss Rob Campbell says the government has "choked" on its reforms of the health system, and its lack of clear direction has contributed to many leaving the sector.
He also claimed some managers deliberately slowed down change, and were against the reforms happening at all.
But the government said it was committed, and change will take time.
In a speech on Monday night the former Te Whatu Ora chair took aim at the agency, saying the reform package has turned out like a "half-baked cake".
Campbell said it was a case of the "same old, same old", with too many indecisive managers who do not listen to workers.
He was sacked from the health agency last month for making political comments about the National Party's stance on co-governance.
Campbell told Morning Report there were too many substantial and damaging holes in the reform packages that had been put together by consultants and government advisors.
"We're in a health crisis, let's be clear about that," he said.
"And so people working within the system need certainty and they need support.
"They need to think that the government and Te Whatu Ora are on their side. There needed to be a whole lot more involvement with the existing organisations and people involved in the system, meeting their immediate needs."
Health Minister Dr Ayesha Verrall said the government had been working "very hard" on health reforms and it would take time for them to come to life. She said Campbell was entitled to his views and to share them.
Campbell said reforms were "gradually inching" forward, but one of the biggest issues within the sector was high levels of distrust by staff - causing many to either leave the system, not come in at all or work in the private sector.
Spending years "degrading a system" meant reforms would not turn it around instantly, but Campbell said there needed to be a clear path forward laid out, and steps to improve it straight away.
"With that level of clarity I think we would have stopped the number of [people leaving] and would have also attracted more people, because they would have been able to see a system going places where they could define their roles in it.
"The big holes that were left, the uncertainties that were left, have been a real big problem for the reform so far."
Campbell told Morning Report there were people within management positions who would "deliberately" slow down processes of change to save their own jobs.
"Many people in those sorts of roles didn't believe in the reforms in the first place," he said.
"I don't think it was the majority by any stretch of the imagination but I don't think there is any doubt about that and I think, for example, the Ministry of Health who didn't have its role all that clearly defined in the legislation has spent a lot of time trying to ensure that it retains a high degree of power and influence over things and Te Whatu Ora is quite limited in what it has freedom to do."
Campbell said the government did not have the intent it claimed it had to carry through and provide the level of funding and support required to make drastic changes to the health sector.
"The government choked on it," he said.
As former chair, Campbell said he took responsibility for issues within the sector to an extent, but he did not have the power some may think he had.
"I felt I wasn't actually having quite as much influence as I should've, but I didn't volunteer to be sacked.
"I'd rather still be in there fighting the good fight but it was the government's decision to have me outside the tent, pointing in the other direction."
Verrall said the government had was determined with the reform to see the change needed for the health system.
"It needs to be more equitable, services need to be more convenient and near where people live.
"I can only speak to my experience which is that I've seen a lot of collaborative work to get the change we need in the system."
Verrall said the reforms needed time to come to life.
"It is a hugely complex project, and we're only part of the way through it and I have very high ambitions for them and I'm committed to seeing them through.
"The health system is saving lives better than many other systems in the world but there are pressures on our staff and people do have to wait too long for services, and I'm focused on fixing that."
Verrall said the government was "completely committed to the direction of the reform. It will take time, and I'm determined to work to see it through."
Te Whatu Ora declined Morning Report's interview request.