Teenagers wanting to have a civil union or de facto relationship will soon require approval from a judge.
Parliament is considering a bill in the name of National MP Joanne Hayes which is designed to protect 16 and 17 year-olds from forced marriage in New Zealand.
It will require them to get consent from a Family Court judge rather than their parents.
MPs on the Justice Committee have unanimously backed the bill after public hearings, and also decided to extend it to other legal relationships.
The committee's report said civil unions and de facto relationships provided many of the same legal protections as a marriage and including them in the legislation would avoid potential loopholes.
Some MPs on the committee expressed concerns that the law change would make legal recognition of de facto relationships less accessible.
"Balanced against this, however, we recognise that requiring court consent for de facto relationships would help to protect 16 and 17 year-olds from being forced into any legally recognised relationship.
"Because the law generally treats legal relationships the same, a de facto relationship could be exploited in ways this bill aims to prevent if it were excluded from the requirement for court consent."
Under existing law, 16 and 17 year-olds who wish to marry only need parental consent. Around 30 people of this age marry a year, mostly female, and Hayes' bill aimed to prevent them being married against their will.
At its first reading, Hayes told Parliament that child marriage and forced marriage were "the most horrific culture practices that could happen".
"There are horrific stories that I have heard to do with forced marriage and child marriage that just absolutely sicken me, and we must ensure that they must stop here in New Zealand before they get legs and carry on," she said.
"We know that some girls also are exported to New Zealand for the purposes of forced marriage. All this has to do with a fee to parents, a bit of a story given to the young woman who is told, 'you come over here, you'll get free education, we'll look after you'.
"And they end up as slaves in an unwanted marriage and one that ends in violence, to the point that we hear stories of where young women lose their lives, and there is no justice for them."
The bill was initially put in the private member's ballot by former National MP and Equal Employment Opportunities Commissioner at the Human Right Commission Jackie Blue, who handed it over to Hayes when she left Parliament.