Boatpeople policy tarnishes rights record - UN

Canberra sends asylum-seekers trying to reach Australia by sea to isolated outposts on Nauru and Papua New Guinea's Manus Island, with the detention camps' conditions widely criticised by refugee advocates and medical professionals.

Following an 18-day mission to Australia, UN special rapporteur Francois Crepeau said migrant rights had deteriorated under current government policy.

"The punitive approach adopted by Australia towards migrants who arrived by boat has served to erode their human rights," he said.

"It is a fundamental principle of human rights law that one person cannot be punished only for the reason of deterring another."

Asylum-seekers who arrive by boat are blocked from being resettled in Australia even if found to be genuine refugees in a hardline stance Canberra says is a crucial deterrent to people-smugglers.

The government has defended its position, including turning boats back, as necessary to stem waves of migration by people from war-torn Afghanistan, Sri Lanka and the Middle East, with many dying at sea during the treacherous journey.

Crepeau, who visited detention facilities in Australia and the camp at Nauru, acknowledged that Australia had the right to deny entry or return migrants.

But it "equally has an obligation to respect the human rights of all migrants in the process," he added, voicing "deep concern" about the impact of mandatory and prolonged detention on mental health.

The offshore camps have become a political headache for Canberra, which this month announced a "one-off" deal to settle an unspecified number of the 1,600 boatpeople held at Nauru and Manus Island in the United States.

There is now concern the agreement could be scuppered by the election of Donald Trump, who campaigned to ban Muslim immigration.

While cautioning that some of Australia's migration policies and laws were "regressive and fall way behind international standards", the UN rapporteur commended the country for increasing its refugee intake and welcoming 12,000 refugees from Syria.

But he also noted that xenophobia and hate speech seemed to have increased "creating a significant trend in the negative perceptions of migrants".

"Politicians who have engaged in this negative discourse seem to have given permission to people on the street to act in xenophobic ways and to allow for the rise of nationalist populist groups," he said.

"Australia must work to fight xenophobia, discrimination and violence against migrants, in acts and speech."

Earlier this year, anti-immigration politician Pauline Hanson was re-elected to parliament where, in her first speech since returning, she warned Australia was in danger of being swamped by Muslims.