The Coalition government’s campaign against the refugee medical evacuation laws is based on “mistruths” and “vindictive point-scoring”, the former president of the Australian Human Rights Commission, Gillian Triggs, says.

On Friday Triggs was appointed United Nations assistant high commissioner for protection, working with the UN high commissioner for refugees, Filippo Grandi.

Grandi said Triggs would bring “extensive expertise, knowledge and vast experience in international refugee protection” to the role.

In Triggs’ five-year term as AHRC president, which ended in 2017, she faced a combative government that took umbrage at her criticism of its treatment of refugees and asylum seekers held on Manus Island and Nauru.

The Coalition government is now trying to repeal legislation that was passed against its wishes earlier this year that allows refugees held on Manus and Nauru to be brought to Australia for medical treatment. The medevac repeal bill has been referred to a committee and will not be voted on in the Senate until November.

In an interview with Guardian Australia on Sunday, Triggs said that public debate on migration policy, particularly around the medevac laws, was at an impasse.

“It does seem to be stuck, and stuck on the basis of mistruths. When [the home affairs minister, Peter] Dutton was challenged over how many of these people were criminals, he couldn’t come up with any. It’s outrageous that [the government] should make comments that are factually untrue to distort an argument,” she said.

“The government clearly was deeply offended at the capacity of other parliamentarians to get the medevac bill through. I think it’s a little short of vindictive point-scoring now [that] we are going to get rid of it.”

Triggs said with or without the legislation, the government was bringing some refugees to Australia for medical care, and the medevac laws had been “modestly successful”.

“The sky has not fallen in, and nothing terrible has happened, and we’ve delivered urgent and necessary medical care to people who needed it.”

Triggs said the debate in Australia on refugee policy had regressed to such an extent that the public would tolerate the politics of withdrawal of the medevac legislation.

“It’s an illustration of how we are stuck, but we are stuck in a deeply inhumane and illegal policy,” she said. “I don’t really see that changing in the short term, unfortunately.”

Triggs said her new role at the UN was to encourage governments across the world to live up to their refugee protection obligations.

“We need to ensure that those that are carrying the burden are supported by others with the responsibility,” she said. “Refugees flood in their millions to parts of Africa, parts of Latin America, and across Europe, and we’ve seen a particularly egregious example of the Rohingya leaving Myanmar for Bangladesh.

“I understand there are a million refugees being hosted by Bangladesh; now Bangladesh is exceptional in its generosity in providing protection and safety but not all countries do that.

“Some countries try to put up walls, try to turn boats and people back to get that level of protection. The burden globally is really imbalanced, and tragically much of that burden is being taken up by some of the poorest countries in the world.”

Triggs said to convince governments to meet their refugee protection obligations, the discussion around migration and border control needed to be separated from the discussion around people fleeing persecution and war.

“Of course the nation-state has a right to protect its borders and a right to determine its migration policy,” she said. “Unfortunately we see in the political debate politicians see an advantage in conflating the two.”

Triggs was concerned by other countries viewing Australia’s offshore detention policy as appealing, including the United States, which has been keeping asylum seekers in detention camps.

“It is obviously very worrying that some countries are pointing to Australia as having an approach that they think is worth emulating,” she said. “You can’t stick your head in the sand.”

Triggs said she was hopeful the Australian prime minister, Scott Morrison, who is the architect of the current offshore detention regime, would “bring it back to the sensible middle” as public sentiment shifts.

“I think it’s in his interests that he does it because the Australian public view is changing and I think it would take the matter off the political agenda and help him get back on with what he wants to do, which is manage the economy and create jobs.

“He has it in him to adopt a more humane policy, and he’s practically won the election single-handedly and he has an enormous mandate and power, and he should use it to bring back Australia to policies that the Australian people are much more comfortable with.”