Mr Morrison said that in the 100 days since the September 18 start of Operation Sovereign Borders, an average of 145 asylum seekers had arrived on three boats a fortnight.
That compares with about 920 people on more than a dozen boats a fortnight between the introduction of the previous government's regional resettlement arrangement with Papua New Guinea and the start of Operation Sovereign Borders.
Critics say the policy is inhumane, while the United Nations Human Rights Commission has pointed to deficiencies in the running of the asylum seeker processing camps on Nauru and in PNG - including unhygienic conditions and limited processing of asylum claims.
Mr Morrison said he had been aware of a 92-page letter from 15 doctors employed at detention facilities that highlighted a low standard of medical care at the detention centre on Christmas Island.
He said Australia would continue to send asylum seekers to Christmas Island, while International Health and Medical Services and his department would investigate the claims made in the letter.
Mr Morrison said last week a family of asylum seekers, including an intellectually disabled woman, would be reunited in community detention so she could be properly cared for by her relatives.
He said there would be improvements to Australia's offshore processing facilities.
- AAP