The Children's Commissioner is even more concerned about the deportation of a 15-year-old from Australia, now that he's had a briefing.
Judge Andrew Becroft sought information about the case after the deportation of the minor was made public earlier this week.
Foreign Affairs Minister Nanaia Mahuta was notified last week of the boy's imminent deportation.
The boy has family here, but little information has been made public about the teen to protect his privacy.
The minister says the circumstances of the case are very complex, but has signalled he is not a 501 deportee.
When asked yesterday, Mahuta said New Zealand has had no advice suggesting Australia had breached any international law.
However, Children's Commissioner Andrew Becroft did not believe Australia had stuck to its international obligations under the Convention on the Rights of the Child.
"It is the most signed convention in history, we can't play fast and loose with it.
"I think there is every reason to conclude, on what I know at the moment, that while two countries have signed that convention only one is really applying it and abiding by it," he said.
Judge Becroft said the briefing he has received has left him even more concerned than he already was.
"Why put him on a plane by himself, without support to a country that I understand, we need to check this out, he has never been to before.
"By any analysis it seems to me to be outrageous on what we know so far and it needs to be taken up by the highest authorities and I understand it is being," he said.
Those concerns were echoed by Australian Lawyers Alliance's Greg Barns.
Australian authorities have indicated that the minor may have voluntarily been deported from Australian shores.
But Barns has vetoed that as a possibility.
"To deport a child of 15 years of age is always involuntary, whatever the child may say.
"There is a total inequality of power here, you've got the frightening force of the Australian border force and a young child and to say the child has consented to the action I find just extraordinary," he said.
He said the convention clearly indicated the best interest of the child needs to be put first.
The convention also states no child should be subjected to cruelty.
Barns said he could not see how Australia was acting in the child's best interests.
"Children are put in immigration detention and whilst they might be separated from adults they're in a facility that is completely inappropriate for children. It has none of the rehabilitative mechanisms or the care that is required.
"To then be shunted on a plane with border force security would be a frightening experience for the child," he said.
He said New Zealand needed to take a stand.
"It is getting to the point where the contempt with which Australia treats New Zealand in relation to this issue both with adults and now with of course children are at such a level that New Zealand needs to be taking strong action against Australia, including making complaints on the global stage," he said.
A spokesperson at the Minister for Children Kelvin Davis' office said any questions about Australia's decisions were a matter for the Australian government.
In the meantime they said Oranga Tamariki had been working extensively with authorities both in Australia and New Zealand to "support this young person's arrival".