Sacked defence minister Chris Penk has returned to Parliament but is refusing to confirm or deny whether he challenged the National Party leader.

Christopher Luxon won a second vote of confidence two weeks ago, and told reporters Penk had been stripped of his portfolios after he mounted a leadership challenge.

Penk will not contest his Kaipara ki Mahurangi seat at the November election, but is continuing to work as an MP until then.

He arrived in Wellington on Tuesday morning to meet with his former ministerial staff, and despite being welcome to attend his party caucus, he has chosen not to.

Penk told media he would return to caucus next week, and said it had been humbling to receive messages of support from both sides of the House.

Asked if he had tried to roll the prime minister Penk, said he was "looking forwards, not backwards".

"I've got no comment on the events of a couple of weeks ago, I've turned up to Parliament to work for the good people of Kaipara ki Mahurangi, which is what I was sent here originally to do and that's what I'm going to do from today onwards."

Penk told reporters he wasn't aware of much of what had been said or reported about his sacking and the events leading up to it.

"The Prime Minister makes appointments, and the reverse in terms of ministerial roles. He's perfectly entitled to do that, he's explained that he's done that and his reasons for it and of course it's not for me to second guess it."

Penk said he had "very good relationships" inside the National Party caucus.

"'I've been really fortunate that a number of people from across the political aisle, both past and present, have been generous enough to reach out, and that's been yeah really humbling actually."

It is usual for retiring MPs to make a valedictory speech before leaving, but Penk said he hadn't decided whether he would.

"Members don't always give a valedictory. Enough's been said, I think, the last couple of weeks, including an urgent debate, an hour of the time of the House of Representatives devoted to my fate, which is, I think, enough."

Penk said he was "sure" National MPs were fully behind the prime minister but it also wasn't for him to speak on behalf of them.

Asked if the public had been told the full truth about what happened two weeks ago in the three-hour long caucus meeting, he said "I haven't seen all the reports, I'm not responsible for them".

"I know from my point of view, clearly my own circumstances have changed, and I'm perfectly comfortable with this," Penk said.

"I'm perfectly happy where I am now. I'm in a comfortable space. I'm going to be a good local member of parliament for the people of Kaipara ki Mahurangi."