The report claims the Australian and New Zealand governments are "threatening the very survival of some Pacific nations" by putting forward emission reduction targets inconsistent with keeping a global temperature rise below 2 degrees.
The report accuses the two governments of failing to respond to the "wake-up call" of Cyclone Pam's devastation of Vanuatu six months ago and catastrophic flooding in Kiribati and Tuvalu earlier this year.
It expresses doubt about whether either country will "do the right thing" by the Pacific and back a strong commitment on climate change in Port Moresby.
Mr Abbott, who did not attend last year's forum, is expected to fly to Port Moresby on Wednesday and return late on Thursday.
Pacific Island countries have pushed for a commitment to a goal of limiting the average global temperature rise to 1.5 degrees above pre-industrial levels, insisting that the current goal of 2 degrees is woefully inadequate.
"Australia and New Zealand must substantially increase their current emissions reduction targets," says Oxfam Australia's chief executive, Dr Helen Szoke, who will attend a three-day meeting of non-government organisations in Port Moresby before the leaders' summit.
"But they also need to provide clarity on how they will meet their international climate finance commitments and help ensure vulnerable communities in the Pacific can access the support they need."
Several Pacific leaders, including the Prime Minister of Tuvalu, Enele Sosene Sopoaga, the President of Kiribati, Anote Tong, and Fiji's Prime Minister Frank Bainimarama, have been highly critical of Australia and New Zealand on climate change.
Marshall Islands foreign minister Tony de Brum has branded Australia's "weak target" - of reducing domestic emissions by 26-28 per cent below 2005 levels by 2030 - as a serious blow to the reputation of "our big brother down south".
The meeting is expected to consider endorsing a Moresby Declaration for an effective global climate agreement in Paris that has been proposed by the Pacific Islands Climate Action Network.
It will also consider establishing a regional fact finding team to investigate reports of "ongoing gross human rights violations" in West Papua in response to a submission from more than 40 civil society organisations in 13 Pacific countries and territories.
The submission cites recent videos leaked and distributed on YouTube that "capture gruesome footage of separate incidents where West Papuan are being tortured by Indonesian soldiers".