Of the close to 1600 people being held in immigration detention centres across the Tasman, 199 of them are Kiwis, new figures show.
New Zealanders are now the biggest group by nationality in Australian detention centres - making up 12.6 percent of detainees - followed by Iranians.
The figures from the Australian Department of Immigration and Border Protection also show 1375 people are being held in mainland detention centres, while just over 200 are at the notorious Christmas Island facility.
Labour's corrections spokesman Kelvin Davis says the new figures should spur the government into action.
"Now that New Zealanders are the biggest group in the immigration detention centres, the government surely must acknowledge that they've underestimated the problem," he said.
"National has to step up and start doing something positive for people who are being treated unfairly and often brutally and inhumanely."
The number of Kiwis in detention centres has been on the rise since Australia brought in tough new immigration rules in late 2014.
Under those rules, any non-citizen who has been sentenced to 12 months or more in prison, or fails a good character test, can have their visa revoked.
Because of the special category visa most New Zealanders enter Australia under, they're not eligible to apply for residency.
The issue has been raised at the highest levels, with Prime Minister John Key discussing it with his Australian counterpart Malcolm Turnbull.
Nationalities in immigration detention in Australia
(as at June 30, 2016)