Morrison declares Western Australia will decide who wins the coming election
"Then they'll get their fish hooks into the legal system, long after any medical treatment has been done, and they'll remain often in community detention which requires us to actually go and provide housing," Mr Morrison told SBS News on Christmas Island.
Doctors are yet to recommend any asylum seekers or refugees on Manus Island or Nauru for medical treatment in Australia under the new medevac process which was made law on Friday.
The government plans to send anyone approved under the new laws to Christmas Island, spending up to $1.4 billion over four years to upgrade medical facilities to cater for 500 people.
Some who require more serious treatment could then be sent to a public hospital on the mainland.
Mr Morrison backed Home Affairs Minister Peter Dutton's claims last week that that would mean other Australians would be forced to wait longer.
"If someone's coming for medical treatment in a public hospital and they're getting a treatment in that hospital, well there's a finite amount of support.
"I mean, if they're in an operating theatre, that's an operating theatre someone else could be in, I think that's a fairly simple fact."
More sensational claims
Home Affairs Minister Peter Dutton on Thursday 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.