Lawyers acting for hundreds of asylum seekers at the Manus Island detention centre are launching a High Court bid that could result in their transfer to Australia.
Solicitor Matthew Byrne told AAP the legal team was also seeking an urgent injunction to prevent their 757 male clients being sent to Nauru after Papua New Guinea closes the centre to abide by a domestic court ruling.
The Australian case will argue there had been violations of human rights, and seek compensation for the men.
A spokesman for the High Court said the legal action revived an existing case.
The matter has not yet been listed.
Officials from Australia and PNG are still working on a plan to deal with the centre's closure and the fate of asylum seekers there.
'Horrendous prisons'
Asylum seeker and journalist Behrouz Boochani has written an open letter to Immigration Minister Peter Dutton criticising the government's offshore processing policy.
He also slammed for the recent self-harm attempts, including self-immolation, by asylum seekers on Nauru.
"I would tell you openly, the one who deserves blame is you, yourself, no one else," he wrote.
"As a person who has lived under this dictatorial system for years, I would tell you that this language and this type of targeting the civil society, media and human rights activist[s] is the language of dictatorial system and dictators.
"Surely you know better than others that Reza, Omid, Hamid, Fazel, Hodan and many other are the victims of your cruel and inhuman policy controlling prisons."
Mr Boochani wrote that the offshore processing policy would "disgrace Australia".
"Mr Minister, only, and only, the history will judge your words and your accusations targeting the civil society," he wrote."
"I should also mention that when the offshore processing policy ends, your political era will also end."
