A private member's Bill to have the Family Court oversee all marriages of people under the age of 18 is being backed by UNICEF.
National Party MP Jo Hayes is concerned young people, particularly in migrant communities, are being forced into marriage.
"It's around about that cultural marriage thing that we've really got to nip that down, because of course marriage can be hidden in a cultural marriage."
UNICEF executive director Vivien Maidaborn says the law change makes sense.
"It's a really sound way of having an overview of a cultural practise that's really common in other parts of the world, but we don't want here in a way that finishes up with girls or boys being abused."
There are fears girls as young as 10are being married off against their will.
"We need to resource organisations like Shakti, the Asian women's refuge, so that they can develop the networks to find those girls early and support them escape those arrangements," says Ms Maidaborn.
Last year 36 girls and 12 boys aged 16 or 17 were married. Ms Maidaborn says those are just the ones we know about.
"There are a whole lot more where there's a cultural acceptance the marriage is real, but there's no formal, legal marriage. We don't know how many of those there are, and we need to."
Shakti agrees the numbers don't tell the whole story about what proportion of underage marriage could be forced, but say Family Court consent would be a good stopgap measure.
"I think one marriage is reason enough to do it, isn't it? So we shouldn't put numbers on that," says Shakti advocate Wendy Vyas.
In September, the Government announced it would make forced marriage illegal in a raft of law changes around family violence.
Justice Minister Amy Adams doesn't believe it's prevalent enough to lead to many prosecutions.
"We have to be careful not to over-criminalise families who are working in a perfectly lawful and appropriate way, so I think we'll see how this plays out and I think at this stage the settings feel about right."
She says there's a more pressing concern.
"What I am very conscious of and mindful of actually is immigration status being used as a weapon of control in family situations, and we certainly do see evidence of that and that is what we are very mindful of in our family violence reforms."