A Papua New Guinea lawyer says all men detained on Manus Island by Australia are eligible to claim compensation through his case.
Last week, the PNG Supreme Court upheld the right of Manus detainees to seek damages for the breach of their constitutional rights including the deprivation of liberty.
The ruling followed the court's decision in April 2016 that their detention was unlawful.
In September, the Australian government agreed to pay $US50 million in compensation to Manus detainees, and it was suggested men receiving that payout would not qualify for further damages.
But the lawyer Ben Lomai said that was not so.
"The course of action in Melbourne was based on common law tort which means they can sue for civil wrongs such as torture," said Dr Lomai.
"That is very different from the case we are doing here in the Papua New Guinea Supreme Court (where) the course of action is based on a constitutional breach," he said.
"Everyone who have passed through Manus at some point in time are entitled to claim."
Dr Lomai said 731 applicants were currently joined to his case and he intended to add "two or three hundred" more, including men now in Nauru and the United States as well as those deported and repatriated.
The Australian government would be liable for any damages awarded by the PNG Supreme Court, according to Dr Lomai.
"There is a current agreement between the Australian and PNG governments which says that any costs associated with legal proceedings will be met by the Australian government," he said.
"That's how I see it, and I've been reliably informed by PNG Immigration that Australia will pay for all the costs associated with these proceedings."
Dr Lomai said this week he would file for directions from the court to have the parties agree any disputed facts "before we can set the matter for trial."
"But if there is no real disputed facts then the parties should consider settling the matter," he said.
The lawyer said the compensation case was next due before the court on February 5 for a directions hearing.
In terms of the damages he would seek, Dr Lomai said as a starting point he intended to claim 1000 Kina ($US311) for each applicant per day of detention.
"It's up to the court to decide to reduce that amount," he said.