Prime Minister Jacinda Ardern says Labour has acknowledged it failed the teens alleging sexual assault.

Labour's party president says the most "comprehensive review" of a political party ever seen will be carried out by an independent barrister on the back of sexual assault allegations.

Nigel Haworth has spoken to media in Auckland alongside Prime Minister Jacinda Ardern where he has apologised to the four teenagers who were allegedly sexually assaulted at a camp near Waihi last month.

"I want to start by saying how seriously we are taking this matter. We understand we failed in our duty of care during the event...and in support we've offered since then," Haworth said.

"We are very, very distressed about this and want to apologise deeply to the four people and their families...and the other people who took part in this camp."

READ MORE:

* Victim tells Labour they have gone to police over alleged sexual assault

* Second sexual assault allegation surfaces for Labour Party

* Sexual abuse support organisation says Labour right not to tell parents

Neither Haworth or the party's general secretary Andrew Kirton will be resigning in light of how the allegations were handled in the days and weeks after the camp.

The comprehensive review of the "whole party and its behaviours" will be carried out by senior barrister, Maria Berryman, who has experience in investigations, in particular dealing with sexual assaults.

Ardern said "we handled this very, very badly as a party".

"The general secretary himself has acknowledged there were failings in place."

SIMON MAUDE/STUFF Labour Party President Nigel Haworth fronts the media.

She said Young Labour "should never have been left in this situation".

Labour has suspended all events run by its youth wing following the alleged sexual assault at a summer camp last month.

Haworth said, "we're not stopping them forever" but they won't restart until "safety can be guaranteed".

FACEBOOK/YOUNG LABOUR Labour's General Secretary Andrew Kirton addresses young supporters at this year's 'Summer Camp'.

He acknowledged "a lot of responsibility" had been given to Young Labour following the camp and "events overtook that responsibility".

Everybody who took part in the Waihi camp would be spoken to, to ensure they feel supported, Haworth said.

He had been with the party for four years and had never before heard of an incident like it, he said.

Labour MP Liz Craig was at the camp and was asleep when the sexual assaults took place.

She posted on Facebook on Wednesday that she stayed overnight because she couldn't get a flight home on the Saturday after being invited to speak to attendees on oral health issues.

"On the Saturday evening I attended a quiz event and went to bed early once this had finished.

"While alcohol was present, I understood the organising committee had put in place measures to ensure those under the age of 18 were not drinking, and that organising committee members had been designated to oversee the evening's events," she posted.

"I was dismayed to hear of events being raised in the media this week, as I was unaware until then that anything of this nature had occurred."

On Wednesday there were photos still on Ardern's Instagram page of the summer camp, including of attendees.

She said she would take those photos down immediately.

ALCOHOL BAN FOR YOUNG LABOUR

The party has banned alcohol from all events where those under 18 are present and a senior member of the Labour Party will be present at any future Young Labour events.

The bans come after a 20-year-old man allegedly sexually assaulted four teenagers, all aged 16, including putting his hands down the pants of at least three of them.

There was alcohol present at the camp, despite some of the attendees being underage.

The Young Labour supporter was ejected the morning after the alleged incidents took place, and barred from future events.

However, there was a delay in the Young Labour organisers alerting party officials to the incident, and in the party offering support to the victims. Professional support and counselling, as well as an explicit offer to facilitate going to police was not made until last week - more than three weeks after the incident took place.

On Tuesday, one of the victims told the party they had reported the incident to police.

And on Wednesday, police told the public they had launched an investigation into the alleged assaults.

Kirton said he had also been contacted by another victim, who said she had been subjected to a similar assault at a Labour event in the past 10 years.

Kirton and Ardern both acknowledged the party had been too slow, and not explicit enough, in its offer of support to the victims.

Ardern said the party had failed to provide a safe environment for young people at the Waihi Summer Camp, and to properly deal with serious concerns raised by several attendees in relation to sexual misconduct and alcohol.

"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.

"Given that a complaint has now been laid with the Police I cannot comment on the specifics, but I want to reiterate that we did not do the right thing fast enough in dealing with these incidents.

"Our young party members are our future. They work hard for our cause and we must ensure they can do so in a safe and supportive environment," Ardern said.

The party was reviewing its practices and polices, in conjunction with Sexual Abuse Prevention Network.

Meanwhile, Kirton would be making contact with all attendees at the camp to apologise and offer any support they needed.

Haworth had not fronted media about the incident until Wednesday, when he said all Young Labour events had been suspended while the party reviewed issues around how best to create "the safest possible environment at all our events".

"Notwithstanding the findings of the review, we have decided that alcohol will not be allowed at any future events where those under 18 are present. In addition, the Party will run summer camps in the future," Haworth said.

WHERE TO GET HELP

Rape Crisis - 0800 88 33 00 (24hr service), click link for information on local helplines

Victim Support - 0800 842 846 (24hr service)

The Harbour - online support and information for people affected by sexual abuse

Women's Refuge (Females only) - crisis line available on 0800 733 843

Male Survivors of Sexual Abuse Trust (Males only) - Helplines across NZ, click to find out more

Wellington HELP (all genders) - 04 801 6655 - 0 for the 24/7 crisis line

Auckland HELP (all genders) - 09 623 1700 for the 24/7 support line

If you are in danger, or are being subjected to sexual violence, call 111.