Almost one in 10 people now being held in Australian detention centres is a New Zealand citizen, the second largest nationality being detained.
An Australian lawyers' group said the number of New Zealanders being locked up and deported could eventually run into the thousands.
The latest figures, for the end of August, showed New Zealanders account for 9.1 percent of those in detention, second only to Iranian visa-holders and asylum-seekers.
Altogether, 184 New Zealanders are being detained.
Eighty have already been deported since new laws came into force in Australia last year.
Australian Lawyers Alliance national president Greg Barns said immigration officials could eventually round up many of the 5,000 New Zealanders who have served more than 12 months in Australian jails.
He said 1,500 New Zealanders were currently imprisoned, but many of those deported or facing deportation completed their sentences a long time ago.
"They've moved on with their lives - they've become very, very good members of the community, they have strong ties to Australia and in fact they have no ties to New Zealand.
"Australia's suddenly turning around on a whim and saying, 'well, despite all of that, we're going to kick you out and back to New Zealand'."
Mr Barns said it was bizarre that Christmas Island was being used to detain New Zealand immigrants (There are 75 New Zealand and Pacific Islanders, according to detainees Radio NZ has spoken to).
"It was previously used for asylum seekers who were seeking to come to Australia, and that was why it was established. There's no rhyme or reason as to why you'd use the most remote immigration facility in Australia."
He said New Zealand was the hardest hit of any country under the new policy and deportees had no right of appeal.
He said the suspected suicide of a New-Zealand-born man being held in a high-security prison pending deportation had brought the issue into the Australian media spotlight.
Meanwhile, the Ministry of Foreign Affairs said the Ministry and consulates were receiving a small number of enquiries each week about New Zealanders held in detention in Australia.
But it has declined to say whether it was providing consular support to citizens in Australia who face deportation back to New Zealand, citing privacy reasons.
The ministry said most New Zealanders in Australia did not seek consular assistance because they already had well-established support networks or employed legal assistance.