A report by the United Nations High Commissioner for Refugees says Australia's processing centre for asylum seekers on Papua New Guinea's Manus Island puts it in breach of human rights conventions.
A UNHCR team visted the centre last month and found conditions there to be harsh and inadequate - findings that mirror those of a visit to the Nauru refugee facility.
The Regional Representative, Richard Towle, says the people being held on Manus Island are suffering a serious deprivation of liberty.
"It's one of the most important international human rights commitments. Habeas corpus should be available for people who have been unlawfully detained or to have it challenged and at the moment there isn't an appropriate system in PNG available for people to challenge the basis of their detention, which has led us to the regrettable conclusion that currently it's an arbritary detention regime."
Richard Towle says he expects the governments of Australia and Papua New Guinea to take the report's recommendations seriously.