A royal commission into the abuse of teenagers at a NT juvenile detention centre is expected to start in September and be limited to the territory.
A royal commission into youth detention abuse will be limited to the Northern Territory, with Malcolm Turnbull warning a broader inquiry could lose its way.
Despite calls for the investigation to be wider, the prime minister says royal commissions are most effective when their terms of reference are clear and focused.
"Royal commissions with sweeping terms of reference that go on for years and years often lose their way," he said on Wednesday, later warning a nation-wide inquiry would take years.
Mr Turnbull expects the inquiry into the abuse of young men, especially at the Don Dale centre in the Northern Territory - where some boys were stripped naked, tear-gassed and held in solitary confinement - to start as soon as September following a directions hearing in August.
A report should be due early next year.
Mr Turnbull agreed with acting Labor leader Tanya Plibersek who said all politicians should share responsibility for the treatment of young people in detention.
"There is no doubt that some of the mistreatment has occurred in the territory under Labor governments," Mr Turnbull said.
The NT Chief Minister Adam Giles and federal Indigenous Affairs Minister Nigel Scullion have come under fire over their knowledge of the abuse, with both insisting they weren't aware of the incidents before they were aired by the ABC's Four Corners program.
Ms Plibersek believes Senator Scullion has been "completely inadequate" in the portfolio but said blame shouldn't solely be laid on him.
"He's not the only person who's let these kids down," she said.
"We each need to bear a share of responsibility for it."
The Giles administration also needed to take responsibility but she stopped short of calling for its sacking.
"I think it's a big call to say that a state or territory can't govern itself even with a catastrophic failure such as this."
The opposition says the royal commission should be extended to other states if a case is made for a broader inquiry.
Draft terms of reference will be taken to cabinet on Thursday.
Treasurer Scott Morrison said it was important to have a well-targeted inquiry to ensure it found a solution.
But setting up the royal commission was no small exercise.
"You can be sure that the cabinet will give due consideration to all the things that need to be included and what it needs to focus on predominantly," he said.
Meanwhile, the lawyer for one of the teenagers seen shackled to a mechanical device chair for two hours and flung across a room in separate incidents, is calling for his immediate release from a Darwin adult prison.
Peter O'Brien says some of the guards who brutalised Dylan Voller at Don Dale were now working in the same centre he's being kept.