The UN special rapporteur has given his preliminary take on Australia's migration system following an 18-day visit.
For all the good work in increasing the humanitarian refugee intake and welcoming fleeing Syrians, Australia's punitive approach towards boat arrivals is tarnishing our human rights record.
That's the takeout from United Nation's special rapporteur Francois Crepeau at the end of his 18-day visit to Australia and Nauru.
He has commended Australia for increasing the annual refugee intake to 18,750 from 2018, welcoming 12,000 Syrian refugees and for the energy shown by those who work with migrants.
"In the human rights doctrine you cannot punish John in order to prevent Bill from doing something."
But Mr Crepeau warns some of Australia's laws are regressive and fall way behind international standards.
"Some of Australia's migration policies have increasingly eroded the human rights of migrants in contravention of its international human rights and humanitarian obligations," he says in his end-of-mission statement, released in Canberra on Friday.
Mr Crepeau called on Australia to stop intercepting and pushing back asylum-seeker boats, saying the practice does not meet human rights obligations.
He questioned the difference in treatment of asylum seekers who arrive by boat with those who come by plane, despite acknowledging the theory that it sends a message to people smugglers.
"In the human rights doctrine you cannot punish John in order to prevent Bill from doing something," he told reporters.
Mr Crepeau reminded detention should at all times be proportional, reasonable and a measure of last resort.
Australia should introduce a statutory time limit on immigration detention, he recommended, having met people who had been held for up to seven and eight years.
The effect of detention on wellbeing was incalculable, he said.
"Many of them are on a regular diet of happy pills in the morning and sleeping tablets in the evening."
Mr Crepeau praised the government for its commitment for getting children out of detention and said it should be committed into law.
He confirmed Australia is responsible for the people it sends to Nauru and how they are treated.
While the centre was now an open facility, it was still detention-like and those on the island nation continued to experience geographical and psychological isolation.
"Australia would vehemently protest if its citizens were treated like this by other countries and especially if Australian children were treated like this," Mr Crepeau said.
He wants asylum seekers to be afforded more legal help, noting they already face extraordinary barriers such as language.
"As much as any of us need counselling when we're doing our tax returns, migrants, refugees, asylum seekers need counselling when they're trying to navigate the immigration system."
Mr Crepeau believes Australia should have a constitutional bill of rights or a Human Rights Act.
He described as good, news of a resettlement agreement with the United States.
"If it results in many or most of the people who are in Nauru and Manus to be settled elsewhere in a place where they can have a future to me that's good," he said.