An interim High Court injunction has been issued preventing the return of 153 Sri Lankans amid ongoing concerns about their safety.
It came just hours after the Government confirmed it has handed over a separate group of 41 asylum seekers to Sri Lanka's military, after being processed at sea.
The Tamil Refugee Council fears the injunction is too late, that the larger boat has already faced the same fate.
Legal scholars say Australia's actions could constitute "enforced disappearance".
Presenter: Rachael Brown
Speaker: George Newhouse, solicitor; Trevor Grant, Tamil Refugee Council
BROWN: The 153 asylum seekers, wherever they are, have been given a 24-hour lifeline.
The High Court has granted an interim injunction stopping the Australian Government from handing them over to the Sri Lankan navy.
Solicitor George Newhouse says the asylum seekers are Tamils who are entitled to have their allegations against the Sri Lankan government heard.
NEWHOUSE: These people are in real fear of their lives, many of them have been subjected to torture and persecution. If Australia was to return the asylum seekers to the Sri Lankan authorities we would be in breach of the refoulement rules and our international obligations on asylum seekers
BROWN: The injunction is in place until this afternoon when the matter will be heard in the High Court.
The asylum seekers reportedly fled Sri Lanka, to a refugee camp in India, then boarded a boat to Australia, which was intercepted off Christmas Island more than a week ago.
The Immigration Minister, Scott Morrison, has admitted another boat, carrying 41 asylum seekers, has already been handed over after being processed at sea.
A Sri Lankan police spokesman says this group will be brought before the court, and anyone found to have left illegally faces two years jail and a fine.
George Newhouse says it's shocking their advocates have to resort to court intervention.
NEWHOUSE: As far as we're aware, this is the first time Australian courts have had to consider a situation where a government is actively handing over people at risk to their persecutors. It's a very serious act, people's lives are at stake.
BROWN: Scott Morrison says the boat is not in Australian waters but won't comment further as the matter is before the court.
The Shadow Minister for Immigration, Richard Marles, says in the meantime, he expects Mr Morrison to abide by the law.
But the injunction may already be too late. The Tamil Refugee Council fears the Australian Navy may have already handed the asylum seekers over.
The Council has tried give this murky situation a face, releasing a photo of three year old Febrina, grinning in a fairy dress and wings.
Febrina's father is pleading with Minister Morrison to reveal the whereabouts of his little girl and more than 30 other children on the boat, one reportedly only 10 months old.
The father has been speaking to the Tamil Refugee Council's Trevor Grant.
GRANT: Over a week ago, families that were on the boat had sent out distress calls that they might've been in a little bit of trouble and they spoke to the families but that was quickly shut down and we suspect that that's because Australian naval vessels or customs people boarded the boat and rendered them incommunicado.
BROWN: Do you know where the boat was then?
GRANT: Well we sense it was certainly in Australian waters, it may have been pretty close to Christmas Island from what we can gather.
BROWN: And do you have any suspicions where it might be now?
GRANT: Our worst fears are that these people have already been put into the hands of the Sri Lankan navy. The father of this little girl said to us if any of them are sent back they are liable to be tortured and possibly even killed. He has told us there's 11 people on the boat he knows of who have been tortured.
Back in 2012 our own foreign affairs department asked the Sri Lankan government - and this was in a forum at the UN - to stop torturing and disappearing people. Now that's a statement of fact from the Australian government that now is sending people back to the same country, it beggars belief.
BROWN: Legal scholars say they fear Australia's actions amount to "enforced disappearance", and that the country is falling foul of a raft of international conventions.
This week Scott Morrison visits Sri Lanka to attend the commissioning ceremony for two former Australian customs vessels gifted to the Sri Lankan government but it's a far smaller boat commanding the region's attention.