The fatal riot at the immigration detention centre on Papua New Guinea's Manus Island continues to drag down the Australian Government, with claims camp guards invited armed locals to join the violence and that Immigration and Border Protection Minister Scott Morrison kept key facts secret.

The riot, which caused the death of 23-year-old Iranian asylum seeker Reza Barati and injured dozens more, has dominated politics since the return of Parliament this week and brought renewed international condemnation of the policy of indefinite, mandatory detention on remote Pacific Islands.

It has fed into polls reversing the Government's brief return to ascendancy after trailing Labor since late last year, adding to rising concerns over Prime Minister Tony Abbott's forecast spending cuts, especially in health and education.

The latest Newspoll reported in the Australian yesterday showed Labor leading the two-party preferred vote by 54-46 per cent, its highest level of support since former Prime Minister Kevin Rudd was ousted by Julia Gillard in 2010.


A new Morgan poll released this week gave Labor a much narrower 50.5-49.5 per cent two-party preferred lead.

The riot and the Government's policies have also gained increasing foreign attention, with reports in major newspapers including the New York Times and Washington Post, Britain's Guardian and Independent, the China Daily, the Jakarta Post, Singapore's Straits Times and the Bangkok Post in Thailand.

Last week the United Nations' human rights office said the camps on Manus Island and Nauru violated international law, describing the policy as "inhuman and degrading".

Amnesty International said the Manus Island violence came as no surprise, with more than 1200 asylum seekers detained indefinitely under "deliberately harsh and humiliating conditions".

"Many of these men have now passed the critical six-month mark, and we know that indefinite detention is a significant contributing factor to the deterioration of the mental health of such vulnerable people who have fled war, terror and persecution," Amnesty said.

Labor has been hammering the Government over the riot, but cannot claim any moral high ground: mandatory offshore detention is also Opposition policy, and violence, including the near-razing of the Nauru camp last year, marked its oversight.

Morrison has said that the inquiry now under way into the Manus violence will also investigate the "hasty" re-opening of Manus Island by Labor when it decided to return to the "Pacific solution" policies of former Liberal Prime Minister John Howard.

Labor MPs and the Greens have called for Morrison's resignation following his admission that earlier claims that the worst violence had occurred after inmates broke out of the camp was wrong. He now says the riot occurred within the centre.

Fairfax newspapers reported yesterday that Morrison had known for days that his initial statement was incorrect, but that he has refused to explain why he delayed his correction.

New claims have also surfaced regarding the conduct of guards employed by contractor G4S, due to be replaced as centre manager by Transfield Services. Guards potentially implicated in the violence will continue to work at the centre under the new contract.

A witness who watched the violence and spoke to the ABC on condition of anonymity said G4S guards opened the camp to allow in locals armed with lengths of wood to help contain the rioters.

"The locals came to see what's happening, they were on the road to see what's happening," he said. "The G4S guards just break the fence down, they told everybody to go in and stop them and hit them and fight them."

Some asylum seekers who sought shelter from the violence in their rooms or the centre's gymnasium were dragged out and brutally assaulted, the witness told the ABC.

The ABC was also told by an anonymous Australian G4S guard that Barati had been hit by lengths of wood and metal poles, and had his head or neck "stomped on".