Prime Minister John Key wants Australia to provide better information about the treatment of people it is deporting to New Zealand.
Christmas Island Photo: Ingo Arndt / FotoNatura / Minden Pictures / Biosphoto
There have been suggestions up to 75 New Zealanders and Pacific Islanders are being held on Christmas Island but Australian authorities refuse to discuss numbers.
John Key Photo: RNZ / Alexander Robertson
Mr Key said he had heard anecdotal accounts but had no idea how many people might be there.
He said Australia should provide more information.
But Mr Key said he was also worried Australia deported people who had committed very minor offences, and he intended raising the issue with new Australian Prime Minister Malcolm Turnbull.
"There are people that are potentially going to be deported to New Zealand now, under the new rules Australia are implementing, that are at a very low threshold of criminal activity but [have] no community of interest with New Zealand."
He said they had probably moved to Australia as young children, had been educated there and had no family left in New Zealand.
Mr Key said it made no sense to send those people to New Zealand.
Labour Party foreign affairs spokesman David Shearer said Australia should remember the long-standing bond between the countries when holding New Zealanders in its detention centres.
He said New Zealanders and Australians had fought side by side, and a better deal was needed.
"They are able to do this but the question is, is this the right thing to do? It seems to me that the domestic issues and problems that Australia are facing are being dumped on New Zealand."
Under the new rules, which were introduced late last year, anyone who is not an Australian citizen and has served more than a year in prison in their lifetime is liable for deportation.
The latest figures show 166 New Zealanders are being detained and face deportation. This makes New Zealanders the third largest group being held in Australian detention centres, with only Iranians and Sri Lankans topping them.
New Zealanders did not feature in the top 10 source countries for detainees until six months ago, after the new rules were introduced.
Australian judge shocked at NZ man held on Christmas Island
Otago-born Jason Wereta, who is being held on Christmas Island, for driving offences and assault said his case had shocked an Australian judge.
Mr Wereta has lived in Australia for 17 years.
He said he was jailed for driving while disqualified, and assault.
But in April this year he was taken into custody by immigration and sent to Christmas Island, he said.
Mr Wereta said the sudden move meant he did not get to see his wife and three children, who lived on the Gold Coast and who had been planning to visit him.
He had an appeal in the mainland courts; the judge had said she was unhappy at him being isolated on the island and he should not have been sent there.