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.
• Covid 19 coronavirus: Why the United States is on the brink of catastrophe
• Covid 19 coronavirus: What you need to know about Sunday's big developments
• Covid 19 coronavirus: 1-day-old premature infant dies from virus complications
• Covid 19 coronavirus: FMA clamps down on misleading insurance ads
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."
Commuting from Tauranga to Wellington
Bridges defended driving from Tauranga to Wellington for the Epidemic Response Committee, which he chairs, and said he was doing the trip for "essential work for Covid 19".
"I have to be here asking questions, getting the answers and making sure we are putting on the pressure where it's appropriate and constructively with a sense of urgency."
He was asked why he couldn't ask questions over Zoom like the other ministers on the committee and Bridges said he didn't think that would be as effective.
It also wasn't practical to move his family to his studio apartment in Wellington for the duration of the lockdown, he said.
Bridges said yesterday his internet at home only worked 50 per cent of the time.
Today when asked about it, he said it wasn't "anywhere near one of the significant factors" in his decision to commute.
Businesses should stay shut to have a strong lockdown
Bridges said he's changed his position on calling for more businesses to be allowed to open under the lockdown rules.
It was now clear to him that New Zealand needed to get out of alert level 4 as quickly as possible to help the economy to recover on the other side.
"That means having a really strong lockdown."
Petition for mandatory quarantine at the border
Appearing before the Epidemic Response Committee, director-general of health Dr Ashley Bloomfield said authorities were considering quarantining all international arrivals.
Bridges said that should happen immediately because he thought it was now manageable to quarantine everyone coming into New Zealand.
"It seems to me to be an absolute no-brainer. The calls for urgency have been there now for weeks. Let's please get on with it."
Prime Minister Jacinda Ardern said the Government saw the borders as an "ongoing" area of risk and indicated restrictions would ramp up shortly.
The National Party this afternoon launched a petition calling for quarantining to happen immediately.