The Australian Greens are calling for immediate inquiry into the boat tragedy that has left about 50 suspected asylum seekers dead or missing off Indonesia.
Some of the 28 survivors from an asylum-seeker boat that sank 50 metres off the coast of Indonesia claim their pleas to Australia for help were ignored.
They say Australian rescue authorities told them help was on the way, but it never came.
However, Australian authorities say they co-ordinated the initial rescue effort but could not locate the vessel, which sank off west Java.
Senior Labour MP Bill Shorten, a leading candidate for the party's leadership, says the new government has many questions to answer about what happened.
Indonesia says at least 21 people drowned when the boat, which was believed to be carrying about 80 passengers, sank off the coast of Java on Thursday.
The Australian Government says a distress call was received on Friday morning about the vessel and a broadcast to all ships was issued by the Australian Maritime Safety Authority.
But a merchant ship and a border-protection aircraft were both unable to find the boat.
Some of the survivors say as many as 10 calls to Australian authorities were either eventually ignored, or were treated as a low priority.
Immigration Minister Scott Morrison said details of the sinking were unclear and additional information was being sought from Indonesia.
AAP reports Mr Morrison said the sinking reflected the dangers of people smuggling.
"The Australian government expresses its deepest sympathies to those affected by this tragedy for their loss and will continue to provide any assistance required by the Indonesian government," he said.
50 metres from shore
Survivors said the boat returned to Indonesia and sank only 50 metres from the shore.
The ABC reports it sank off Agrabinta, a remote area of the coast off the Cianjur region of west Java after getting into trouble in rough seas on Thursday.
Australian Greens Leader Christine Milne wants an inquiry into the tragedy.
"I would expect that to happen before the next parliament sits," she told Sky News on Sunday.