Asylum-seeker families detained on Christmas Island might be released into Australia if the federal government gets enough Senate support for temporary protection visas (TPVs).

Immigration Minister Scott Morrison signalled a major backdown on offshore processing during an address to the National Press Club on Wednesday.

The government had repeatedly insisted no asylum seekers arriving by boat would reach Australia under its watch.

But the government is now “open to alternatives” such as TPVs for asylum seekers on Christmas Island who arrived between July 19 and the end of December last year, he says.

“A temporary protection visa would ensure that the people smugglers’ promise of permanent resettlement would not have been honoured, maintaining the integrity of the government’s border protection regime,” Mr Morrison told reporters.

He argues the policy would be cheaper than the costly transfer of families with children to Nauru.

Opposition immigration spokesman Richard Marles called it a “monumental backflip” from the minister.

Greens senator Sarah Hanson-Young also seized on the policy U-turn.

“Offshore processing is unworkable and, finally, the jig is up,” she said.

Meanwhile, Mr Morrison hinted that efforts to extend the “refugee resettlement club” to Cambodia and Papua New Guinea may have hit a snag.

But he insists he never underestimated the difficulties that must be worked through with PNG before resettlement can actually begin.

“There’s still distance to travel. It’s frustrating but I’m confident we’ll get there,” he said.

He acknowledged Cambodia needed a lot of help to build up capability.

“This isn’t about just putting people somewhere and looking the other way,” Mr Morrison said.

Negotiations are under way on a deal, but refugees would be sent to Cambodia only on a voluntary basis and would have freedom of movement and work rights.

PNG Prime Minister Peter O’Neill was still “rock solid” in his support for the plan, Mr Morrison said.

He suggested Australia would have no responsibility should refugees resettled there be attacked by PNG nationals.

PNG locals and guards were involved in the February violence at the Manus Island detention centre, which resulted in one asylum-seeker death and scores injured.

Forty-four men found to be genuine refugees are waiting for resettlement in PNG, and 206 refugees are living temporarily on Nauru while waiting for resettlement in a third country, likely to be Cambodia.

Mr Morrison is concerned that if developing countries do not get involved in refugee resettlement, there is a danger that First World welfare will become a selling point for people smugglers.

“The refugee convention and refugee resettlement is supposed to be for asylum seekers, not Centrelink seekers,” he said.

-AAP