Wellington: Prime Minister John Key says he's been "pretty blunt" with the Australian government over the way New Zealanders are being detained and deported.

Mr Key met Foreign Affairs Minister Julie Bishop in New York on Tuesday to raise the issue that is causing increasing concern across the Tasman.

Nearly 200 New Zealanders are being held in detention centres in Australia, facing deportation under new immigration laws that mean anyone who isn't a citizen and who has served a sentence of 12 months or more can be sent home.