Newsroom have reported that the young Labour members – two 16-year-old girls and two boys of the same age – said a 20-year-old man sexually assaulted them in February this year.
The party’s general secretary, Andrew Kirton, confirmed the alleged offender has been fired and banned from future party events.
“The reason why I didn’t tell the prime minister is the advice I’ve got is it could add more distress when a wider group of people became aware of the incident – we wanted to make sure to protect the confidentiality of those involved,” Kirton told Radio New Zealand.
“We decided not to expand the concentric circles of people who know about this, it can be very traumatic and embarrassing for those that are the victims of this. The advice I had is these young people need to make the choices themselves about who they tell.
“It might be something they want to put behind them.”
Ardern, who is pregnant, added: “I have to think of this from a personal perspective and if it were me and I were the parent, I would want to know.
“I am not going to say that what we did was appropriate in response … We should have brought in the professionals straight away, everyone acknowledges that now.”
Senior cabinet minister Megan Woods is reported to have been the only government figure who knew of the claims, after she was contacted by one of the victims via social media. She, too, did not inform Ardern.