The Democrats are calling for the government to explain David Hicks' return to solitary confinement at Guantanamo Bay.
The party's Foreign Affairs spokeswoman, Natasha Stott-Despoja, says if the Attorney-General, Philip Ruddock knows why, he should tell the detainee's father and his lawyers.
Ms Stott Despoja says the move is suspicious and David Hicks' legal team knows of no reason for it.
"It's usually considered punitive treatment, yet they're not aware of anything David Hicks has allegedly done to deserve this treatment.
"Infact they doubt anything at all. They believe it's to break this young man before he even gets to the military commission, so it's very suspicious," she says.