National is standing by Tauranga MP Sam Uffindell following revelations he was asked to leave King's College due to his involvement in the assault of a younger student.

The party's newest MP has admitted he was kicked out of his boarding school as a teenager for beating a younger student.

In a statement, Uffindell says he punched a 13-year-old boy in the arm and body "multiple times" when he was a student at King's College.

Deputy leader Nicola Willis acknowledges the seriousness of the incident and told First Up her thoughts are with the victim.

But she says Uffindell has changed and is sincere in his regret.

"If I thought that Sam was still the same man as he was when he was a 16-year-old who committed this act then I don't think there would be a place for him in Parliament, however, I see that he is extremely sincere in his regret, in his genuine apology and he has been upfront about what occurred.

"I think there has to be room in Parliament for people who have made serious errors, accounted for them and who are now committed to using their position for good."

National Party deputy leader Nicola Willis says Uffindell has changed since the incident. Photo: RNZ / Angus Dreaver.

Willis says both she and leader Christopher Luxon found out about the assault just after lunchtime on Monday.

The party has confirmed the incident was raised during the candidate selection process, saying it reflects a "serious error of judgment" by a then-teenager.

The panel was made up of local and nation party members, Willis says.

It decided he shouldn't be precluded as he had accounted for the actions, was 16 at the time and a different person now, and was apologetic, she says.

"That's a party matter, that's their judgement and where I stand on this today is that I have advised Sam that what he should do now is be completely upfront with New Zealanders about this because ultimately it is the people of New Zealand and the people of Tauranga who will be the judges on this."

"I'm conscious here that we are talking about very serious behaviour by a 16-year-old and as a teenager, many of us would have made serious mistakes."

The idea of her 12-year-old son "being subjected to bullying of this nature is deeply upsetting", she says.

There is an opportunity for everyone in Parliament to ensure they use their positions to "say no to this kind of thing" and to be leaders who condemn it.

"I fully expect that Sam will join me in that condemnation."

The party wouldn't be distracted by these issues, she says.

Asked by RNZ if he will be staying on as an MP, Uffindell says he will be having talks today in Wellington about his future.

-RNZ.