The Morrison government is close to securing support from Senate crossbencher Jacqui Lambie to repeal the so-called medevac laws.
Senator Lambie said on Wednesday afternoon she recognised the government's concerns about the laws which give doctors a much greater say in bringing refugees in from offshore detention to Australia for medical treatment.
She has proposed a single condition in exchange for her support but has not revealed publicly what that is.
"If that condition is met, I will vote in favour of the repeal of medevac," Senator Lambie said in a statement.
She said the condition was a "sensible and reasonable proposition" that she believed the government would be able to meet.
The Tasmanian senator said she supported the government's strong border protection policies.
"I do not believe this position is undermined by the presence of medevac. But the government has made clear to me that it has concerns with the way that medevac is functioning. I recognise those concerns."
More than 150 refugees and asylum seekers have been transferred to Australia from Nauru and Papua New Guinea for medical treatment under the new legislation which was passed against the government's wishes in February.
Senator Lambie's position will come as a blow to refugee advocates and medical professions that have lobbied hard to save what they describe as "life-saving" laws.
Amnesty International said there should be no conditions on the lives of refugees, again urging Senator Lambie to save medevac.
"People are literally being evacuated out of life-threatening conditions that the Australian government put them and continues to hold them in," Amnesty International Australia refugee advisor Graham Thom said.
"Critically-ill people need to be assured they can access the life saving treatment they require to survive. Nothing more, nothing less.”
Senator Jacqui Lambie says her support for the government's bid to repeal medevac is contingent on one condition. Source: AAP
Human Rights Law Centre legal director David Burke welcomed Senator Lambie's acknowledgement of the importance of the laws to the needs of sick people who remain offshore.
"We call on her to make sure that her primary consideration is the humanity of these people and the need to ensure they are able to live safely,” Mr Burke said.
Earlier on Wednesday, advocates presented a petition signed by 5,000 doctors urging Senator Lambie to vote against the government's repeal bid.
Home Affairs Minister Peter Dutton has argued refugees and asylum seekers can exploit the laws to get to Australia.
While Mr Dutton has refused some medical transfers on national security grounds, he has argued the legislation has limited his powers to turn away transferees over criminal history and character concerns.
The government had planned to bring on legislation to reverse the February changes for a vote in the Senate this week, but Senator Lambie's statement indicates more negotiations may be required for the government to secure her crucial vote.
Labor, the Greens and Centre Alliance are standing by the medevac laws, arguing they are working well, while One Nation and Cory Bernardi have declared they'll vote with the government.
