No disciplinary action was taken after an internal investigation looked into the complaints, but the party has now ordered an independent review of how that was conducted following further complaints.
The staffer is understood to still be at work.
The victim, who cannot be named for legal reasons, said the latest revelations showed that nothing had changed since the review of party processes following the Young Labour camp, which led to a person being charged with indecent assault.
"They clearly haven't changed anything, which just makes me angry," said the victim, who says he was one of the summer camp victims.
He added that he did not have much faith that the party's processes would have changed, given that no heads rolled over the summer camp incident.
"It was supposed to be fixed. I didn't have much faith that it would be, simply because the fact there was no accountability. No one lost their job. The report wasn't even released," the victim told the Herald.
"I wasn't confident things were going to change. I hoped they were, but clearly that's not the case. It actually sort of hurts to see this coming out again and to see people dealing with it again.
"For a party whose main line is based on wellbeing and all that sort of carry on, this is just ridiculous. The party leadership is just useless."
Prime Minister Jacinda Ardern said this morning that the party had "absolutely" learned from the incident at the summer camp, and the current review was a chance to see what, if anything, the party should do differently.
"This has been a test of whether or not we've now learnt from that, and the party's taking a good look as to whether or not we're satisfied with the natural process of justice and whether or not we've supported the complainants as we should have."
She was not aware of any complaints made to the police or to Parliamentary Service, which employs parliamentary workers, adding that it would be appropriate for people with complaints "of that nature" to take them to the police.
Speaker Trevor Mallard, who is responsible for Parliamentary Service, said complainants should take any allegations to the police or to the employer.
"Neither I nor the Parliamentary Service have received any complaint against anyone currently working for the Parliamentary Service."
It is unclear who is conducting the independent review, or when Ardern was first told about the allegations.
According to the Labour Party constitution the party can take disciplinary action for a number of reasons, including if the principles, rules and policies of the party are contravened, or if the party is brought into disrepute.