Wellington lawyer Maria Berryman has been brought in to lead the external review of party procedures.
She will also be open to look at any historic allegations of inappropriate sexual behaviour at party events.
Haworth said the party would talk to everyone who was at the Waihi summer camp.
"We will make this party one that is absolutely safe."
He said he had not offered to resign, not did he intend to. He said it was his job to ensure safety for party events.
He defended general secretary Andrew Kirton as one of the best the party has had and he did not expect Kirton to resign, even though his handling of the incident could have been better.
Ardern said she "cannot hand on heart rule out that this hasn't happened before", which is why the changes that have been announced are necessary.
Labour MP Liz Craig was at the Waihi summer camp, but was asleep when the alleged offending took place.
Ardern said there were parental consent forms, but they did not protect the young people at the camp - which is why Young Labour would not be running the camps in the future.
She had not spoken to the victims.
She said the way the party had handled the allegations was poor.
"This is us taking ownership of the issue," she said in relation to the steps announced today.
The review will ensure it doesn't happen again.
She said it was handled badly, but the intent was never to allow harm to be done. "But it was because as we had said, we made mistakes."
Ardern said she did not know of any drug use at the summer camp, and police could look into that as part of its investigation.
She did not know who the alleged offender is.
She has heard a first name, was not familiar with who the person is, and understood the offender was not a party member.
She denied that the party had tried to sweep the incident under the rug, saying that the party was taking ownership of the issue.
She said the offer of support to the victims should have been "made very clear" from the beginning, including support for laying a police complaint.
"It's not appropriate that we left it up to Young Labour to run this event."
She said she was happy to remove photos from the camp from her Instagram account to protect the youths that had attended the camp.
She said she couldn't say if other sexually inappropriate behaviour had taken place at other party events, but the steps announced today were about ensuring a safe environment at future events.
Haworth said there was no timeline for the review at this stage. Ardern said the outcome will mean a change in party policies.
'We need to support them'
Young Labour events will be suspended until a safe environment can be guaranteed.
Ardern and Haworth announced the suspension - and conceded Labour had failed to provide a safe environment for camp attendees.
"As a result of the incidents at the Waihi Summer Camp we have taken the decision to immediately suspend all Young Labour events," Haworth said.
"We need to take the time to properly review issues around how best to create the safest possible environment at all our events.:"
Police confirmed this morning they are now investigating claims of sexual assaults at the camp last month.
It is alleged a 20-year-old man sexually assaulted four teenagers, all aged 16, including putting his hands down the pants of at least three of them at the Young Labour summer camp in Waihi last month.
Haworth also announced that alcohol will not be allowed at any future events where there are people under 18 present. He said an independent review alongside the Sexual Abuse Prevention Network would take place to ensure the safest possible environment in future.
"As a result of the incidents at the Waihi Summer Camp we have taken the decision to immediately suspend all Young Labour events," said Haworth.
"We need to take the time to properly review issues around how best to create the safest possible environment at all our events.
Haworth said that Labour general secretary Andrew Kirton will be making contact with all attendees at the Waihi Summer Camp to apologise - and offer any support they need.
Haworth apologised for putting "too heavy a responsibility on our Young Labour leaders to deal with the aftermath of these incidents".
"I apologise for that. We need to support them too."
Ardern said the party had failed the young people who reported the sexual misconduct, and apologised.
"It has become very clear to me the extent of our failure to both provide a safe environment for those 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."
Ardern said she could not comment on specifics because of the complaint that has now been laid with police.
"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."
Haworth said a "comprehensive external review will be undertaken by a respected independent person shortly working alongside the Sexual Abuse Prevention Network. This will review our policies and procedures in relation to these events including those by Labour's sector groups, and also Waihi.
"The external expert will also be available for anyone who wishes to raise issues in relation to previous events."
