Australian Prime Minister Tony Abbott has said the country is "sick of being lectured" by the UN over its treatment of asylum seekers.
It comes after the special rapporteur on torture said some aspects violated the convention against torture.
Australia detains all asylum seekers who arrive by boat, holding them in offshore processing camps.
Rights groups have criticised conditions on Manus Island, where asylum-seekers are held.
In a new report to be tabled to the UN Human Rights Council on Monday, the rapporteur, Juan Mendez, investigated allegations of torture and abuse in more than 60 countries.
In Australia, he highlighted some cases where the authorities had failed to provide adequate detention conditions, end the detention of children, or prevent escalating violence and tension at Manus Island.
This meant Australia had violated the right of the asylum-seeker to be free from torture and cruel, inhuman or degrading treatment, the report said.
The Australian government has rejected the report.
When asked about the UN's findings, Mr Abbott told reporters: "I really think Australians are sick of being lectured to by the United Nations, particularly, given that we have stopped the boats, and by stopping the boats, we have ended the deaths at sea."
He said hundreds had drowned at sea as the people-smuggling trade flourished under the previous government.
Mr Abbott said stopping the flow of people coming to Australia by boat, mostly through Indonesia, was the "most humanitarian, most decent, the most compassionate thing you can do".
"We have stopped the boats and I think the UN's representatives would have a lot more credibility if they were to give some credit to the Australian government for what we've been able to achieve in this area," Mr Abbott said.
When asked about conditions on Manus, Mr Abbott said: "All of the basic needs of the people on Manus Island are being met ... everyone's needs for food, for clothing, for shelter, for safety are being more than met."
One of the allegations investigated by Mr Mendez is the intimidation and ill-treatment of two asylum-seekers after they gave statements about violent attacks at Manus. He found their rights were in fact breached.
He also found that two government changes to immigration legislation risk violating international laws prohibiting torture.
The report found violations in more than 60 other countries including in the US for the 30-year imprisonment of a mentally ill man on death row.
It also raises alarm at the proposed deportation of several individuals from the UK to countries that engage in torture.
Australia and asylum
- Asylum seekers - mainly from Afghanistan, Sri Lanka, Iraq and Iran - travel to Australia's Christmas Island by boat from Indonesia
- The number of boats rose sharply in 2012 and early 2013. Scores of people have died making the journey
- To stop the influx, the government has adopted hard-line measures intended as a deterrent
- Everyone who arrives is detained. Under a new policy, they are processed in Nauru and Papua New Guinea. Those found to be refugees will be resettled in PNG, Nauru or Cambodia
- Tony Abbot's government has also adopted a policy of tow-backs, or turning boats around
- Rights groups and the UN have voiced serious concerns about the policies and conditions in the detention camps. They accuse Australia of shirking international obligations.