Simon Bridges and deputy Paula Bennett will be challenged for the leadership of the National Party.
Bridges' position is in question after a political poll showed support for National had plunged.
He said he and his deputy, Paula Bennett, are being both being challenged, and he was confident he had the support of the majority of caucus.
He would not say who the two challengers were.
Bridges said the challenge would happen "at the latest" next Tuesday - the day the National Party caucus meets.
The latest Newshub Reid-Research political poll has National with just 30.6 percent support, and in the preferred prime minister's stakes Bridges is on 4.5 percent. At the same time Labour and Jacinda Ardern are enjoying a huge surge in popularity.
"A couple of my colleagues want to challenge myself and Paula Bennett for the leadership and deputy leadership of the National Party," Bridges told Morning Report.
"We've got to resolve that quickly so we can get back to focusing on what matters, and that's Kiwis, your livelihoods and aspirations."
Bridges was "very confident" he had the numbers and that he and Bennett would win, he said. He did not expect any further challenge.
"The overwhelming majority of the caucus are behind me."
A second poll is due out this week, and Bridges said he would not resign, even if it had similar results.
He was not surprised at the polls, he said. because governments had received wall-to-wall coverage during the Covid-19 pandemic.
"You go back four months, a situation where not many had heard of Covid-19, more than that, National was in a position to govern on polling.
"The world over, from Donald Trump to Boris Johnson to Scott Morrison, governments have got a really big boost out of Covid-19 ... the management of that. Here in New Zealand there's been wall-to-wall coverage of the lockdown and government, and health aspects of that.
The country was now moving to a time where it needed to deal with the economic future and the party had a plan for jobs and growth.
Asked whether the more people saw of Jacinda Ardern during this time the more they liked her, Bridges said the prime minister was a likeable person. "My view of politics is it's not just a popularity contest, it's a contest of ideas and policies and plans and the ability to deliver."
Former National MP Bob 'The Builder' Clarkson, who used to hold Bridges' Tauranga seat, is still backing him as leader.
"He's well educated, he doesn't swear like me. So I think he's a decent sort of guy, actually," he said.
"He might not pick the right subjects to talk about sometimes but generally I think he's a nice guy. He's a family man and everything.
"But the leader of the Labour Party has had a charmed run as a politician - she's on the TV 90 percent of the damn time, and that's hard to beat."
Some voters in Bridges' home suburb of Matua concede National's leader has made mistakes but, for the most part, they're forgiving.
"Aside from what I believe was a mistake very early on in the pandemic when it became a little political, I think he's done very well," said one man.
"I guess a lot of the things that the government's done and proposed probably aren't too dissimilar to what National would have done. He just really hasn't done a very good job of - if there's an alternative - getting that across," said another.
One Tauranga voter said he could come across as "a bit bombastic".
"Oh my goodness, just speak to someone - you're not speaking at someone all the time and always having to get your point across. He doesn't seem to listen very well," she said.
"I don't always like what Jacinda Ardern does, but because she comes across as genuine I think that's what makes her the winner."
In the safe National seat of North Shore, it was hard to find anyone with a positive thing to say about Bridges.
"I'm a long-standing National voter and I wouldn't vote for him. I like the ol' Crusher," said Marjory, with a laugh, referring to National MP Judith Collins' nickname.
Peter Bedford said one of Bridges' problems was that he wasn't memorable.
"Three of us were talking the other day and none of us could remember his first name, which is quite brutal."
Bobby Barker from Devonport said Bridges seemed to like being the contrarian.
"I think he doesn't really have any opinions of his own - his opinion is whatever is the dissenting opinion. I don't think he's once come across as honest or anything, just disingenuous."
Rose Hunt from Takapuna said she "just can't listen to him".
"Simon Bridges, he needs to go. He needs to go - a bit like Donald Trump needs to go."
Former National Prime Minister Jim Bolger is promoting Bay of Plenty MP Todd Muller.
"Todd has the ability to work well with all across world, across the line. He's not that harsh partisan position, he will work with others to achieve the right goal," he said.
Simon Bridges and his party are now faced with crucial decisions three months out from the general election.