Winston Peters has fired his first shot at Australia on Tuesday as Acting Prime Minister over its detention of a Kiwi minor in an adult detention centre.
Mr Peters said Australia isn't living up to the UN's convention on the Rights of the Child.
The Melbourne Immigration Transit Accommodation detention centre in Melbourne has been a 17-year-old Kiwi boy's unwanted home for months.
Being surrounded by adults and separated from family violates the UN's rights of the child.
"This person is regarded as a child or a minor, and I'm just reminding the Australians you're a signatory - live up to it," Mr Peters says.
But an Australian minister disagrees, and has fired back at Mr Peters.
"I reject that. Australia has obligations which we meet and my primary obligation is to the Australian public to keep them safe," says Home Affairs Minister Peter Dutton.
The teenager was pulled from juvenile detention and brought without warning to the centre in March.
"It's similar to being in a prison except the conditions are worse, he doesn't have any access to proper healthcare, psychological care or education," says freelance journalist Rebekah Holt.
But Mr Dutton says the teenager is welcome to go jump on a plane anytime.
"If he wants to go back to New Zealand today I'll facilitate his return today," he says. "We don't want him here in Australia."
Mr Dutton claims the child is dangerous, but the teenager's lawyer says the minister is twisting the truth.
"He is telling lies, and I use that term advisedly," argues the teen's lawyer, Greg Barns.
"Peter Dutton is trying to paint a young person who has an unremarkable juvenile justice history as a threat to Australia. It's pathetic."
The Ministry of Foreign Affairs and Trade has expressed its concerns to Australia, and Mr Peters' comments add more pressure still.
But Australia doesn't budge on immigration and the teen could spend months in adult detention whichever way his deportation hearing goes next week.