Labour has suspended all events hosted by its youth wing as police launch an investigation into allegations of sexual assaults at one of the party's summer camps.
But while the prime minister says the matter has been handled "very, very badly", no one will be resigning.
Newsroom this week reported a 20-year-old man allegedly assaulted or harassed four 16-year-olds - two males and two females - by putting his hands down the pants of at least three of them during a party at the camp near Waihi on February 10.
Police on Wednesday morning confirmed an investigation had commenced into the claims.
Later in the day Labour president Nigel Haworth announced all Young Labour events would be suspended immediately pending a probe, saying the party was "distressed", and deeply apologetic.
"We failed in our duty of care," he told reporters in Auckland.
"A comprehensive external review will be undertaken by a respected independent person shortly."
Newsroom reported there was a "mountain" of alcohol at the Waihi event - run by the youth wing - despite a large portion of the attendees being under 18 years old.
As a result, liquor would also be banned outright from all future events where underage teens were attending, Mr Haworth said.
"In addition, the party will run summer camps in the future," he said.
"We gave to the Young Labour leadership in that camp a lot of responsibility and events overtook that responsibility."
Earlier, Labour general secretary Andrew Kirton said he had received a second complaint about separate incident at an event several years ago.
Anyone else who wished to raise issues about previous events could come forward to the review expert, barrister Maria Berryman, Mr Haworth said.
The man accused of the Waihi assaults - not believed to be a member of the party - was ejected from the camp afterwards.
But Mr Kirton didn't inform the teens' parents or Prime Minister Jacinda Ardern about the incident - saying it was a matter of confidentiality.
The party has confirmed list MP Liz Craig was at the camp at the time of the incident, but says she was sleeping.
Questions have also been raised about why a follow-up offer of professional support for the teens took three weeks, with Ms Ardern saying the situation had been handled "very, very badly" by the party.
"We failed the young people who told us they had been hurt - this failure left them feeling abandoned and I am deeply sorry for that. It's not good enough, we let them down," she said.
"I want to reiterate that we did not do the right thing fast enough in dealing with these incidents."
Asked whether he or Mr Kirton would be stepping down over the handling of the situation, Mr Haworth was emphatic no one would be resigning.
"Our focus as a party must be those young people, rather than focusing on the future of individual employees," Ms Ardern told reporters.
Police have declined to comment on details about complaints but have called for anyone with information to come forward.
While the teens had originally not wanted to go to police, one had lodged a complaint this week, Mr Kirton told media.
THE TIMELINE AS WE KNOW IT:
* February 9, 2018 - Prime Minister Jacinda Ardern speaks at the opening of Young Labour's "Summer School" camp in Waihi.
* February 10 - A 20-year-old man allegedly sexually harasses or assaults four 16-year-olds - two males and two females - during a camp event.
* February 11 - The man is thrown out and the victims offered support. Shortly after Labour's general secretary Andrew Kirton is informed.
* March 3 - Follow-up offer of professional help offered to victims, according to Mr Kirton.
* March 4 - Energy Minister Megan Woods receives complaint about lack of response by Young Labour and contacts Mr Kirton, who says the matter is being dealt with "appropriately".
* March 12 - Newsroom publishes the allegations and Ms Ardern is blind-sided by media questions. The party issues a statement saying it is "extremely disappointed" about the incident and launches a review.
* March 13 - Ms Ardern accepts the party was too slow to offer support but says she won't sack Mr Kirton, who later reveals he's been told a second incident at another camp years earlier.
* March 14 - Police confirm they are investigating the allegations and the party suspends all Young Labour events pending a review.