The United Nations refugee agency is critical of conditions for asylum seekers on Nauru.
A report issued by the UN High Commissioner for Refugees says the Australian government's arrangements fail to meet international protection standards.
The ABC reports an agency team spent three days inspecting the facilities earlier this month. It found confusion about the roles and responsibilities of Australia and Nauru, and no functional or fair system for conducting refugee assessments.
The inspectors also questioned the capacity of the island's health services to properly deal with an increase in mental health concerns.
The report also said conditions at the temporary processing facilities are congested and harsh, with little natural shelter from the heat during the day. The report said is exacerbated by the significant noise and dust coming from the construction of permanent facilities.
Amnesty International and the Australian Human Rights Commission have issued similar findings about the Nauru detention centre.
Despite the latest criticism, Immigration Minister Chris Bowen said the federal government remains committed to establishing a permanent detention facility on Nauru.