Prime Minister Christopher Luxon has removed Chris Penk's ministerial portfolios.

"Chris Penk launched a leadership challenge this week, which resulted in today's confidence vote. This makes his role untenable and as such I have removed his portfolios," Luxon said on Wednesday.

Paul Goldsmith will pick up the Defence, Veterans, Space, GCSB and NZSIS portfolios.

Simon Watts will become Minister for Building and Construction.

Earlier on Wednesday afternoon, Luxon held a press conference where he announced he had survived the second attempt to oust him this year.

In a brief statement to media, Luxon said he had the full confidence of the National Party caucus before leaving without answering questions.

"Our caucus is united, and it is determined to win this election," he said.

"Our focus is on National's positive plan to fix the basics and to build the future, so that we realise the incredible potential that sits in this country, and that we set it up for our kids and our grandkids."

He was flanked by senior MPs, including Nicola Willis, Mark Mitchell and Chris Bishop.

Standing just behind them was Erica Stanford, who was rumoured to be gunning for the top job.

Penk, ranked 14th on National's list published at the weekend, had earlier denied any involvement in a leadership challenge, after Politik and the New Zealand Herald reported he was doing the numbers for a bid by Stanford.

Upon arriving in Wellington on Tuesday night, Penk said he had confidence in Luxon and would support him in any vote.

"I've always expressed confidence in the leader. Now is no different."

He would not confirm if anyone had called him about the leadership, saying he would not disclose private conversations, but said reports of his involvement as an instigator were "wrong".

He stuck to that position on Wednesday morning, again saying he had confidence in Luxon, and suggested people might be making up stories about him making calls for Stanford.

"I think everyone else needs to get their story straight because I'm hearing multiple different versions. None of them are true, and as I said, I'm not prepared to disclose private conversations, except only to say I have confidence in Christopher Luxon."

Penk had only been promoted to the Cabinet in April, following the retirement of Judith Collins.

He has been an MP since 2017.