Churches have taken the extraordinary step of offering sanctuary to asylum seekers facing deportation in the wake of a High Court verdict, raising the prospect of police raids on places of worship and possible charges for clergy.

Ten Anglican churches and cathedrals have invoked the ancient Christian tradition to offer protection to the 267 people - including 37 babies - facing imminent transfer to Nauru after the court on Wednesday upheld the legality of the government's offshore processing regime.

The movement is being led by the Anglican Dean of Brisbane, Dr Peter Catt, who has declared his St John's Anglican Cathedral a place of sanctuary.

Dr Catt said if any asylum seekers sought sanctuary in his church he would do his best to keep the authorities out. He said he fully accepts that he and other clergy could be charged with obstruction and potentially even face possible jail time.

"We are aware it's a high-risk strategy," he told the ABC.

Dr Catt called it an extraordinary step that would attract the attention of church communities around the world.

The sanctuary principle has its roots in the Old Testament and was once enshrined in English common law but its legality has never been tested in Australia.

"This is a hugely significant action for any Australian church to take. Historically churches have afforded sanctuary to those seeking refuge from brutal and oppressive forces," Dr Catt said on Thursday.

"We offer this refuge because there is irrefutable evidence from health and legal experts that the circumstances asylum seekers, especially children, would face if sent back to Nauru are tantamount to state-sanctioned abuse.

"This fundamentally goes against our faith, so our church community is compelled to act, despite the possibility of individual penalty against us."

Other cathedrals and churches offering sanctuary include Pitt Street Uniting Church, Gosford Anglican Church and the Wayside Chapel in NSW, St George­'s Anglican Cathedral, St Cuthbert's Anglican Church and Wesley Uniting Church in Perth, Pilgrim Uniting Church in ­Adelaide, St David's Anglican Cathedral in Hobart and Christchurch Anglican Cathedral in Darwin.

Dr Catt called it a "fledgling movement".

"What we expect to happen in the course of the day and the next few days is that many churches from many denominations will sign up," he said.

The sanctuary offer came as the United Nations urged Australia to put the interests of children first.

The UN Committee on the Rights of the Child believes Australia has an inadequate understanding of the rights of asylum seeker children.

"This decision by the High Court greatly concerns us as these children and their families face a great risk in being sent to a place that cannot be considered safe nor adequate," said committee chair Benyam Mezmur.

But Immigration Minister Peter Dutton on Thursday said he would not put children in harm's way.

"I've said that we'll provide medical attention as we have in the past to those children that are in need but I also think there is a lot of hype and scare in this campaign in relation to what's happening on Nauru."

Prime Minister Malcolm Turnbull has vowed the government's hardline border stance is unshakable.

Deportations are expected to start occurring within days.

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