Simon Bridges is staying tight-lipped on whether the National Party was involved in Jami-Lee Ross being sent to a mental health facility over the weekend.
"I'm not going to comment on the details, and I'll tell you why: I only learnt about it after the event," Mr Bridges told The AM Show on Wednesday.
"I have some second hand accounts of what has happened, but the reality is I don't know for sure, so I'm not going to engage in that."
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Police arrived at Mr Ross's home early on Sunday morning and he was taken to a mental health unit. It's understood he did not go voluntarily and questions have been raised over whether the National Party was involved in his sectioning.
National Party President Peter Goodfellow also would not answer questions over the party's involvement, telling Interest.co.nz he would not "go into detail of it".
Mr Goodfellow also said he would "let them answer", referring to National MPs, when pressed on whether any National MPs were involved.
"This is a matter to do with one of the MPs though, and given those circumstances, I'll just leave it for somebody else to answer that question," Mr Goodfellow told Interest.co.nz.
But Mr Bridges would not go into further detail, and appeared frustrated by the suggestion of National's involvement in Mr Ross' sectioning. He told The AM Show: "If you're saying the National Party do this, I reject that with every fibre of my being."
He said police and health authorities would "deal with these things, not National", adding, "I only learnt about [Ross's sectioning] after the event".
Mr Ross has made headlines due to his claims the National Party had broken donation laws, as well as allegations he had harassed women in the party, and suggestions he leaked Simon Bridges' expenses.
Bridges confident in National's return
Both National and its leader have taken a hit following the scandal involving Mr Ross.
The latest 1NEWS Colmar Brunton poll shows Labour is now ahead of National in the eyes of the public, while Mr Bridges' ranking as preferred Prime Minister has also dropped significantly.
But Mr Bridges seems confident the scandal will not affect his leadership, telling The AM Show it has been one of the "toughest weeks for National and I think for any leader in living memory".
"I feel personally, I have come through this stronger, and I want to assure the voters I know what we've got to do, and this is to hold this Government to account on a myriad of things they are getting wrong."
"Ultimately, I think the caucus knows, and I think the listeners back home know, that a strong unified party and the party vote is the poll that matters," he said. "That's what determines power, and under my leadership, National's very resilient."
Labour is up 3 percent to 45 percent, while National is down 2 percent to 43 percent, the new poll shows. The Greens have seen a rise, up 1 percent to 7 percent, while there has been no change for New Zealand First.
Jacinda Ardern saw her ratings hit their highest point ever since she became Prime Minister, up to 42 percent, while Mr Bridges' rating fell 3 percent to just 7 percent - his lowest since he became leader. He's now closely followed by Judith Collins on 5 percent.
When pressed on whether he would stand aside if National's polling continues to drop, Mr Bridges said, "I'm not going to get into those things, because under my leadership, that's never going to happen".
"I know over recent months we have strengthened and strengthened because of the weakness of this Government, and the unity and strength of my party," he said. "We will get stronger, and I think you'll see that in the next polls."