The Federal Government will soon move to ban refugees and asylum seekers on Manus Island and Nauru from ever coming to Australia, Prime Minister Malcolm Turnbull says.

Key points: Law would cover those who tried to reach Australia by boat from mid-July 2013

Law would cover those who tried to reach Australia by boat from mid-July 2013 It would block them from obtaining any visa

It would block them from obtaining any visa Refugee advocates fear policy will "push people over the edge"

The new law would cover those who tried to reach Australia by boat from mid-July 2013, and would block them from obtaining any visa, including tourist and business visas.

Mr Turnbull said the legislation would send a clear message.

"This will send the strongest possible signal to the people smugglers ... It is incredibly important that we send the clearest message," Mr Turnbull told a press conference this morning.

"They must know that the door to Australia is closed to those who seek to come here by boat with a people smuggler. It is closed.

"Those passengers will never settle in this country."

The legislation would also apply to people previously held on the Pacific islands but who have since left, including people transferred to Cambodia as part of a $55 million deal.

People who arrived on Manus Island or Nauru as children would be exempt.

Despite the new law, the Immigration Minister would still have discretion to let people into Australia.

Making the law retrospective means it can be used on the nearly 1,300 people who are currently on Manus Island and Nauru.

Seventy-two per cent of those who have been through the camps have been assessed as being genuine refugees, according to the latest Operation Sovereign Borders press release.

'Government takes cues from One Nation': Hanson

One Nation leader Pauline Hanson welcomed the policy, declaring on Twitter that it was "good to see that it looks like the Government is now taking its cues from One Nation. Just like last time".

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But the Opposition accused the Government of making the announcement as a distraction.

"It's a distraction from Peter Dutton's hopeless mismanagement of his portfolio," Deputy Opposition Leader Tanya Plibersek said.

"It is extraordinary that three years on, this Government has not found third countries to resettle those people who are in limbo on Manus Island or Nauru.

"It's time Peter Dutton started doing his job and finding a permanent resettlement option for these people."

Labor MP Andrew Giles asked on Twitter: "What sort of government looks to punish vulnerable people who've sought our help?"

"What is the point of this if the Govt's turn back policy is working? What is this cruel law really about?" Tasmanian Labor senator Lisa Singh tweeted.

Greens' immigration spokesman Nick McKim said Mr Turnbull's policy was a "desperate attempt to reabsorb the votes from Pauline Hanson's One Nation Party".

"Supporting this policy will mean innocent men women and children will be punished for doing nothing wrong," he said.

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 13 minutes 12 seconds 13 m Julie Bishop says the Government needs to send a "very strong message" to those on Nauru and Manus Is.

Policy 'rapidly destroying' refugees, advocates say

Refugee advocates said the plan was unacceptable.

Lawyer David Manne, from the Refugee and Immigration Legal Centre, said the move, expected to be introduced into Parliament next month, would punish refugees.

"The majority of these people are refugees, and the policy is rapidly destroying them," he said.

"This does nothing to address that fundamental question about where they are going to be taken so that they can rebuild their lives in safety and with dignity."

Save the Children said the decision would also cruel the chances of many refugees from reuniting with their families who are already in Australia.

"We know from our past experience working on Nauru that these kinds of announcements can lead to significant unrest and despair among the refugees and asylum seekers who are barely hanging on after spending, in many cases, over three years living in limbo," Director of Policy and Public Advocacy Mat Tinkler said.

"Without offering these children and their families a realistic, humane and viable resettlement option, the Australian Government is only further exacerbating the mental anguish and loss of hope that we have seen build on both Nauru and Manus.

"We have grave concerns that this kind of announcement will push people over the edge."