The head of Australia's Anglican Church, Archbishop Philip Freier, has expressed his "deep concern" over Federal Immigration Minister Peter Dutton's recent cuts to welfare services to about 100 asylum seekers originally brought to Australia from offshore detention for medical treatment.

In his opening address to the church's three-yearly General Synod being held in Maroochydore, on Queensland's Sunshine Coast, this week, the Anglican Primate and Archbishop of Melbourne said the move was "just the latest in a series of decisions to place vulnerable people in even more exposed conditions".

"Of course, it is the responsibility of governments to control national borders," he said. "But as Christians – or simply as people – our most urgent response must come from our common humanity and empathy. It is tragic for these vulnerable people that political parties have hardened refugee resettlement policy and tragic for these few people to be treated in this way."

He said that while refugee policy was an area "about which many politicians would like the churches to remain silent", "it should be a matter of conscience for all Australians that we have kept asylum-seekers in deliberately callous conditions". "Here many of them have suffered trauma and stress, especially defenceless children."

Elsewhere in his address to the 17th General Synod, Archbishop Freier restated his opposition to euthanasia, noting that euthanasia and assisted suicide risked "abandoning those who are in greatest need, who deserve our care and support", and urged Anglicans to vote in the upcoming postal survey on same-sex marriage.

While noting he intended to vote 'no', Archbishop Freier acknowledged that Anglicans held a wide range of opinions on the issue but added that the doctrine of the church - that marriage is between a man and a woman - was unlikely to be revised.

Archbiship Freier also reiterated an apology for the church's response to victims of abuse and highlighted a range of issues, from domestic violence and reconciliation to poverty and climate change, noting that the latter "remains one of the most urgent and intransigent issues facing the church and, indeed, the world".

The synod involves almost 300 delegates from all 23 Anglican dioceses across Australia.