Australia's new asylum policy lacks "adequate protection standards for asylum seekers", the UN says.
Under the new policy, boatpeople headed to Australia will have their claims processed by Papua New Guinea (PNG), and be resettled there if successful.
However, the UN High Commission for Refugees said there were "significant shortcomings" in PNG's legal system for processing asylum seekers.
Thousands of asylum-seekers try to reach Australia by boat every year.
"Australia's Regional Resettlement Arrangement (RRA) with the Government of PNG raises serious, and so far unanswered, protection questions," the UNHCR said in its first review of Australia's new policy.