Opposition leader Simon Bridges agrees with the Prime Minister that David Clark should stay on as Health Minister - for now.
But as soon as the Covid-19 lockdown is over Clark will be gone, Bridges said.
"I think for him having a Prime Minister that doesn't have confidence in him will be fatal."
Bridges also wants mandatory quarantining at the border to be brought in immediately but has changed his position on more businesses being allowed to operate during the lockdown.
Jacinda Ardern announced earlier today that she had demoted Clark in Cabinet for breaking lockdown rules but he would stay on as Health Minister because his role was too important during the Covid-19 crisis.
It was not in the best interests of New Zealanders to remove him but at any other time he would have been sacked, she said.
Bridges said he agreed with Ardern's decision to keep Clark as Health Minister during the lockdown.
"I understand her reasoning on this. I think frankly the Prime Minister was between a rock and a hard place," he told reporters.
"That said, I think the situation one is one that's unsustainable for David Clark post Covid-19.
"We simply can't have a Health Minister - one of our most important roles - at number 20."
Bridges said he thought Clark should "have his feet under the desk" in Wellington where the response to Covid-19 was being led from, instead of being at home in Dunedin.
"I do understand what the Prime Minister is saying though.
"She and New Zealand are in the middle of a health and economic crisis like we've never seen in our lifetimes and so to change ministers right at the moment, I can understand why she wouldn't.
"That said I think his position more medium-term is terminal. He's been demoted, he doesn't have her confidence and frankly, by the look of it, he's not up to it."
Clark today appeared before the Epidemic Response Committee, which is chaired by Bridges and has an Opposition majority, to answer questions as Health Minister and wasn't asked about his questions.
Asked why not, Bridges said: "Frankly I don't want to kick a man when he's down.
"I think we know where things are at. It's a situation where his Prime Minister no longer has confidence in him, he's been heavily demoted and at the end of Covid-19, the crisis we're in, I suspect he won't be minister."