The World Council of Churches has likened one of Australia's detention centres for asylum seekers to the American base for terrorist suspects at Guantanamo Bay.
Speaking after a visit to the Baxter centre in the state of South Australia, the council's general-secretary, Samuel Kobia, said it was like Guantanamo without the shackles.
He said Australia's policy of mandatory detention for refugees arriving in the country illegally was un-Christian and inhumane.
Those entering the country had to be processed, but the authorities were going about it the wrong way, he said.
The government argues that its policy protects Australia's borders and discourages the smuggling of refugees.
The World Council of Churches, which promotes Christian unity, brings together more than 300 churches and denominations.
From the newsroom of the BBC World Service