National Party leader Christopher Luxon didn’t know his newest MP Sam Uffindell viciously beat a younger pupil as a student at a prestigious boarding school before Monday.

Uffindell, who appeared on morning news shows on Tuesday, said he still has the support of his party and the leadership, and that his apology to the man he attacked as a 16-year-old was genuine and wasn't politically motivated.

“I want him to know my apology was genuine and sincere back then and it still is today,” he said. “I own it, I was 16 years old... have learned from it and I am a better person as a result,” he told the AM show.

However, Uffindell concedes he was already in politics, as the chair of the party’s Papamoa branch, before he contacted the man to apologise. He said he got the man's number about a year before he won the Tauranga by-election. Simon Bridges stood down nine months before the by-election.

Uffindell was asked on the campaign trail before the by-election what his biggest mistake was, but didn't reveal the attack. On Tuesday, he said he wasn’t trying to hide from this past.

“That’s [the attack] the dumbest, stupidest thing I have ever done, I’m incredibly remorseful of it.”

On Monday he told Stuff he was upfront to the National Party about the incident during the selection process.

“I was upfront about that. I was really clear about what had happened and detailed it thoroughly. They were very thankful I’d given them full disclosure on that,” he said.

“They were happy that I’d changed from when I was young and I think appreciated I was 16 years old, a stupid teenager that was involved in an incident and had learned a lesson from it. I’m happy they backed me and supported me.”

However, on Tuesday morning Uffindell said he didn’t think National Party leader Christopher Luxon was aware.

“Christopher Luxon wasn’t on the selection committee,” he said. “I am not aware that he was aware of it.”

He said he spoke to Luxon on Monday night, a conversation he described as a brief check-in.

National’s deputy leader Nicola Willis told RNZ she only found out about the attack around Monday lunchtime, but said Uffindell had changed since the incident took place more than two decades ago.

"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."

She said there was room in politics for people who had made mistakes.

Uffindell, who used his maiden speech to critique a “growing culture of lawlessness, lack of accountability, a sense of impunity, and significant underlying generational social problems”, also told RNZ he had empathy for young people who made mistakes.

Credit: stuff.co.nz