An open letter has been sent to Pacific leaders ahead of next week's Pacific Islands Forum meeting urging them to pressure Australia over its treatment of refugees in offshore detention.

The letter, signed by a coalition of 84 international organisations including the likes of Amnesty International, World Vision, Oxfam and the Refugee Council of Australia, says the "cruel and degrading" treatment of refugees and asylum-seekers should be top of the agenda when regional heads of government meet in Nauru next week.

The letter urges Pacific Islands Forum (PIF) leaders to call for an immediate end to Australia's "cruel and abusive refugee" policy under which more than 2000 women, men and children had been detained on Nauru and Manus Island in cruel and degrading conditions over the past five years.

"The Australian Government has repeatedly refused to accept New Zealand's offers to take up to 150 refugees from Manus Island and Nauru, most recently citing the refugee deal with the US as the main reason.

"Regional leaders must show that they will not stand by while the Australian Government's abusive policies continue to risk more lives. It is a stain on the region,"  said Roshika Deo, Amnesty International's Pacific researcher.

Prime Minister Jacinda Ardern, who will attend the PIF meeting next Wednesday, has left open an offer to take 150 asylum-seekers.

Foreign Affairs Minister Winston Peters will be at the meeting on Tuesday and Wednesday.

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Comment is being sought from both Ardern and Peters.

Australian media have been leaked information about children on Nauru apparently giving up on life. Some had stopped eating, drinking and talking, and others were self-harming. Medical staff have been referring dozens of children off the island for medical treatment, with the courts stepping in to override the decisions of authorities declining the transfers.

"The system is clearly broken if children are even considering self-harm," Deo said.

Amnesty International called on the Australian Government to end offshore processing and immediately transfer refugees and asylum-seekers on Manus and Nauru to Australia or to another safe third country.