Former National Party leader Todd Muller says he regrets letting "ego" and "imagined destiny" take over in his political career.

The Bay of Plenty MP, who this morning announced his retirement from politics at the end of the term, spoke candidly with 1News about his decision to step away, with frank reflections on his time in politics.

"Sometimes it's easy in this place to allow your own ego and your own sense of importance and your own sense of imagined destiny to take over.

"That drowns out those better instincts that sit inside you."

He said he did not regret being the National Party leader but "the way it all unfolded".

"Of course you can't help but regret the personal cost for me, but also for my family and in its own way contributed to a cost to the party. You can't unwind that, you can't put a revisionist lens on it, it's what happened. These things come in life and it's how you adjust to it and work through it that counts."

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Ex-National Party leader Todd Muller to retire from politics

Fri, Mar 17

Muller's tenure as leader — just 53 days from May to July 2020 — was a tumultuous one.

He ascended to the role after rolling Simon Bridges, with Nikki Kaye as his deputy. Four National MPs resigned during his tenure, and he courted controversy for possessing a Make America Great Again hat, as well as a blunder by Kaye where she incorrectly said National MP Paul Goldsmith was Māori.

His time also saw a 9% bump in the polls for National, albeit still trailing far behind Labour. He resigned citing mental health and anxiety challenges from the high-pressure role.

On Friday, Muller told 1News there was no one moment that led to his decision to step down after the election.

"I just didn't have the energy for the job. I have in the past put my hands up for things that perhaps I wasn't 100% totally focused for, and it didn't work. When you go through an experience like that, I think you are a little bit more attuned to your own sense of where you are [on] things.

"The pace and the expectations of senior leadership in this place is demanding and I reflected on that and I decided 'look, no, I'll step back and let somebody else have a go'."

He said he had always tried to be honest about his feelings and abilities.

"You always try to bring the best of yourself to a job like this... my experiences over the last two to three years has changed me, I can't deny that. I am more sensitive, frankly, of other people who walk challenging journeys and I'm a whole lot more attuned, I think, to my own capacity, my sense of what I think's doable.

"If you just don't have the energy, you need to do the right thing, and that's where I've landed."

He said National was not a sinking ship and he had "every confidence" National would win the election.

"It's going to be a scrap. I think everybody can see that politics and elections in MMP are always tight wrestles, and this one will be the same.

Asked what was next for him, he joked high on the list was removing his face from a decal on the side of his car — at the entreaty of his youngest daughter.

"She's not particularly rapt with [the decal], for obvious reasons."

He said he had a job to do however as he remained Bay of Plenty MP until the election, and would assist with the election campaign where needed.

At the same time, he would also start considering what his next steps were.

"I love ag, I love trade. Anything export-oriented always lights my fire, so we'll see."

He said he had not been in touch with former employers Zespri or Fonterra.

"They're two companies that I loved working for, but I certainly don't have any expectation to signal a return there."

He said climate change had become a new interest, something he had not known much about five years ago.

Muller said his cross-party work with the Greens' and Climate Change Minister James Shaw on the Zero Carbon Act was "one of the highlights" of his time in Parliament.

"I was... creating some bipartisan support for climate action. Climate change is always going to be unfinished. The next big focus is adaptation and I'm pleased to see that National will be around the table as we reflect on how to do that well for the country."

Asked if he had aspirations of becoming a minister, he said: "Of course it was".

"That's what makes the decision hard. But you've also got to be true to yourself."

He said National Party leader Christopher Luxon had not specifically given an indication as to whether Muller would have become a minister should National win the election, but Muller had felt backed by him.

That was part of the reason he had reversed a decision to resign in 2021, he said.

Muller said his biggest regret from his time in politics was not always following his "gut instinct".

In light of this, he had some advice for budding politicians.

"Follow your passion, but be really clear that like all passions it will take a lot of energy out of you as well. You need to be very clear you're doing it for the right reasons."

A support network was also important, he said.

"It can be a bruising business and it appears to be becoming more so over time.

"It is pretty brutal. It is not quite 24/7, but it is all encompassing, all consuming.

"That's what makes it exciting, because you are giving everything of yourself for a cause that you fundamentally believe will make New Zealand better.

"It's an incredibly rewarding role in that context, but it does have a cost and so you need to be conscious of that when you put your name forward."

He said being an MP was worth it "if you've got the passion to make a difference in people's lives".

"To be effective, you've got to look after yourself as you go through the process."

He said he didn't choose to be a spokesman for mental health challenges but after his "breakdown" — where he resigned from the National Party leadership — he and his wife Michelle decided it was "important to be open".

"Not go on about it, but if anybody ever asked the question just be open, and in being open I have found quite a remarkable response from New Zealanders around the country.

"In probably no small way, looking back, that is a legacy I never would have expected or sought, but it appears people see it as a positive thing."

He said he felt humbled by it.

"It's an emotional thing to talk about, and it's a very raw thing to talk about, and so when you do it so publicly and you see the reaction of people to that it makes you... struck at the scale of similar lived experiences by New Zealanders around the country."

Muller was first elected in 2014, under the leadership of former prime minister John Key.

Rotorua MP Todd McClay will replace Muller as agriculture spokesman, while North Shore MP Simon Watts will take on his climate change role.

McClay would be relieved of the tourism portfolio by Southland MP Joseph Mooney.

Luxon said Muller gave "110% of himself to whatever he does" and said he was a "deep-thinking and hard-working" member of caucus.