Onshore option: Immigration Minister Scott Morrison on Wednesday. Credit:Alex Ellinghausen

In November, Mr Morrison said: "I want to stress all those on Christmas Island who are there now - those who arrived after July 19 will be going to Nauru or Manus Island. There will be no exceptions, whether you're Syrian, Iranian, single, married, adult, child, they will all be going to Nauru or Manus Island and will not return to live in Australia."

But the minister told an audience at the National Press Club that the government was now looking at TPVs as an "alternative" option for the 2700 people, including 450 children, who arrived by boat and many of whom are being held on Christmas Island. He is currently negotiating with crossbenchers in the new Senate to reintroduce TPVs after Labor and the Greens twice blocked the controversial measure that prevents refugees from gaining permanent residence in Australia.

"Now while it will continue to be the policy of the government that anyone who arrives illegally by boat will be transferred to offshore processing … the government is open to alternatives for the earlier July 19 to December 31 caseload, but not those who may arrive now or who have already been transferred," Mr Morrison said in the speech.

"Combined with other measures, TPVs will also give the government an alternative option for those who arrived after July 19 and before the end of last year, including over 450 children. Seventy five per cent of this group, including children, turned up under the previous government and had not been transferred to offshore processing centres."