The use of solitary confinement in youth detention should be outlawed by state and territory governments, a royal commission says.
The inquiry into violence, abuse and exploitation of people with a disability recommended the practice be prohibited.
The commissioners said youth justice legislation should also be amended nationwide to clearly define safeguards applying to the isolation or seclusion of children with disability.
"Solitary confinement exacerbates the difficulties experienced by children in detention who have cognitive impairment and brain injuries," they said.
No jurisdiction prohibits solitary confinement for children, the practice of locking children in their cells for 22 or more hours a day.
The commissioners recommended authorities significantly improve disability screening processes, particularly for Indigenous people.
Governments should ensure timely screening and expert assessment are available for children with cognitive disability involved in the criminal justice system to ensure they receive the necessary support.
The commission found the treatment of children in detention in Western Australia, which included those with a disability, did not meet Australia's international obligations.
They found children with disability who had been detained at Banksia Hill youth detention centre, had been subjected "on a regular basis to confinement in their cells in contravention of their entitlements to out-of-cell time under the Young Offenders Act 1994 (WA)".
Children who had been detained at Banksia Hill gave harrowing evidence to the royal commission.
An Indigenous man, given the pseudonym "Nathan", spoke about how he experienced lockdowns "over and over" and was denied fresh air and sunlight.
First detained from the age of 12, Nathan said on some days he was let out of his cell for 20 minutes, or not at all.
Detention officers had told him "you're a bad kid".
Nathan said his time in Banksia Hill took him to a dark place which ruined his life, leading him to want to take his own life.
Research has found the likelihood of high levels of cognitive impairment among children in youth detention.
The first study to investigate the prevalence of fetal alcohol spectrum disorder, found 36 per cent of children who were in youth detention in Western Australia between May 2015 and December 2016 had the disorder.
The commission recommended changes to the National Principles on people unfit to plead - and to those who are not to be found guilty by reason of mental health or impairment - so they state that indefinite detention is unacceptable.
The commission also recommended repealing any laws that provide for indefinite detention.
