Australia has exchanged barbs with New Zealand over the imprisonment of a minor in adult immigration detention in Melbourne.

New Zealand’s Acting Prime Minister Winston Peters said the Australian government was in breach of the UN Convention on the Rights of the Child by detaining the 17-year-old New Zealand citizen in the Melbourne Immigration Transit Centre in Broadmeadows since March.

Home Affairs Minister Peter Dutton fired back, saying: "If New Zealand want him back, then he's welcome to get on the first flight out.”

New Zealand’s acting prime minister Winston Peters says the Australian government is in breach of the UN Convention on the Rights of the Child. Credit:AP

Mr Peters, NZ’s foreign minister who is standing in while Jacinda Ardern is on maternity leave, said he had raised the issue with the Australian government.