Home Affairs Minister Peter Dutton has argued refugees brought to Australia for medical treatment would soon become citizens, against the wishes of the community.
However, under Australian law, it's entirely up to the minister to grant them citizenship.
This latest warning follows Mr Dutton's sensational claims refugees medically evacuated from Manus Island and Nauru would take up hospital beds and public housing usually reserved for Australians.
"Once they're in Australia you'll never see them deported or leaving our shores, they'll go on to become Australian citizens, and that is not the outcome that most Australians support," Mr Dutton told 2GB radio on Thursday.
Detainees brought to Australia for medical treatment are legally considered "transitory persons", and the minister has full discretion over whether to grant them permanent protection, residency or citizenship.
The federal government has declared only those asylum seekers with serious medical emergencies will continue coming to the Australian mainland for treatment.
All others, including women, will be put in detention on Christmas Island.
"We've made decisions that these people are not coming to Australia. It's been the long-standing position of Scott Morrison and myself and we hold that line," Mr Dutton said.
"But unfortunately, this bill has passed through the parliament."
Under the coalition government, 900 patients and family members have been evacuated to the Australian mainland for health reasons, with a quarter of them arriving since September.
The prime minister took media to Christmas Island on Wednesday to showcase the facilities his government has reopened at an estimated cost of $1.4 billion over four years.
The mothballed complex was revived after the medical evacuation laws that passed parliament, against the government's wishes, made it easier for sick asylum seekers to come to Australia.
The government is also bracing for a potential influx of new boat arrivals, fearing people smugglers will consider the legislative changes a softening of border security.
"The only place they're going to see is the inside of a room at Christmas Island's hardened detention facility," Mr Morrison told reporters on Thursday.
"They won't be walking the streets of Perth, I can assure you of that."
Mr Shorten rubbished suggestions Labor had weakened Australia's borders, taking aim at the government.
"It is beyond a joke that the prime minister of Australia flies to the furthest part of what is technically Australia to run a scare campaign," he told reporters in Melbourne.
"Do you know that photo opportunity which the prime minister took Australia on yesterday cost $2000 a minute?"
Healthcare operations at the Christmas Island detention centre will be expanded to cater for more than 500 asylum seekers.
An extra 60 medical staff, including 35 mental health professionals, will be sent to the remote island off Western Australia, taking the total to 72.
Nobody has so far applied under the new medical evacuation laws, which came into effect on Saturday.
"There will be applications, I have no doubt about it," Mr Morrison told Perth radio station 6PR.
Single males will be housed in the North West Point detention centre, the biggest and most secure complex on Christmas Island.
Women will be held in lower security detention facilities on the island.
