Rotorua MP Todd McClay says the panel that helped pick Sam Uffindell as National's candidate for Tauranga took his admission of an assault at school "very seriously".
It comes as National's new party president Sylvia Wood admits the selection process needs improvement following Uffindell's scandal.
"The selection process was runin accordance with the National Party rules, which require confidentiality," Wood said in a statement.
"However, it is now clear that process could be further improved, and we are looking at how best to achieve that."
In a press conference yesterday, McClay said the pre-selection panel concluded that the incident happened 22 years ago and Uffindell had worked "very hard to be a better person since then".
This week it was revealed that Uffindell, who won the Tauranga byelection in June, assaulted a 13-year-old boy while aged 16 and at Auckland's King's College 23 years ago.
Yesterday Uffindell also revealed he may have tackled other students during the "raid" of the third form (Year 9) dorm, in addition to punching one student several times.
He was asked to leave the college the next day, finishing his schooling at St Paul's Collegiate in Hamilton.
The National Party has also confirmed Uffindell was suspended from St Paul's for leaving the school property without permission to go to a party on a Saturday evening - an automatic three-day suspension.
In a press conference yesterday, Rotorua MP Todd McClay said he was a member of the pre-selection panel and the information about the assault was provided to the panel by the board.
"We took it very seriously and saw it as an incident that needed to be questioned further. The panel questioned Sam for some length of time on this and all aspects of it.
"We then considered it separately and came to the conclusion that it was an incident that he took seriously, that happened 22 years previously when he was 16 years of age and that he had worked very, very hard to be a better person since then."
Asked why he did not advise Uffindell to front-foot the incident, McClay said: "During the campaign, we were very, very focused on the various things that were coming up."
He said Uffindell was regretful and had apologised.
Asked why he did not tell National Party leader Christopher Luxon about it, McClay said it was not his role as campaign chairman to talk directly to the leader about things that happened in the selection process.
Uffindell yesterday said he was a bully and "a 16-year-old thug" while in high school.
He said the attack on the 13-year-old had changed his life, and had an impact on the person he had hit.
"I'm not proud at all. I was effectively a bully. I was a mean person. There will be other people at high school that I have hurt.
"I might have tackled a few people, or punched a few people. As I said, I was a bully at school and I'm not happy with that."
Asked why he hadn't come clean earlier, he said in hindsight that should have happened.
He said he could have been "more forthcoming" about the incident during the Tauranga byelection campaign that he won.
"I was a 16-year-old and I made a big mistake. I've got young children and one day they will be at school, and if stuff like this happened I would be very upset."
National Party leader Christopher Luxon said he was standing by Uffindell, but says he should have been told of the incident earlier.
"He has my backing and he has my support but clearly he needs to build back trust with the voters of Tauranga."
In the Tauranga CBD yesterday, the Bay of Plenty Times asked shoppers about their views on what Uffindell did, whether he should have disclosed it to voters and if he should resign.
Anna Hayns, 60, said the timing of his apology was "suspicious".
"But we're all young and dumb once."
The Tauranga CBD resident said her vote for Uffindell would not have changed if this information was public during the campaign because she voted for "policy rather than the person".
John Delaney, 48, said he was "on the fence" about whether Uffindell should have publicly disclosed this information during his campaign.
"On the one hand, people will form a view on the type of character he is based upon his previous actions.
"On the other hand, it was a long time ago and we should be allowed to make our mistakes and pay whatever the price is and be allowed to still have future careers etc, that aren't damaged by what we may have done when we were 16 years old," the Tauranga Avenues resident said.
"I don't believe people should be made to pay later in life for something they've already paid for once."