The latest report on conditions in Banksia Hill Detention Centre is a validation of the class action being built against the State of Western Australia, advocates say.
The report from Western Australia's Inspector of Custodial Services said children in the facility were subject to "cruel, inhuman and degrading" and called on the Department of Justice to immediately rectify the situation.
Some 70 per cent of those detained in Banksia Hill are Aboriginal.
National Suicide Prevention & Trauma Recovery Project coordinator Megan Krakouer and her colleague Gerry Georgatos have collected the testimonies from hundreds of current and former Banksia Hill inmates to build a class action.
"The report from Eamon Ryan is a validation of the testimonies we have received from children across the state," she said.
"It highlights the inhuman suffering children have endured in this facility. It also highlights the need for more Indigenous staff.
"It demonstrates the need for the class action against the State of Western Australia, to save lives, to improve the life circumstances not only for the children but also for their families on the outside."
Last November law firm Levitt Robinson Solicitors, which is assisting in the prospective class action, wrote to WA Corrective Services Minister Bill Johnston warning Banksia Hill was a "tinderbox ready to ignite".
After the release of last week's OICS report, lawyer Dana Levitt said the problems in Banksia Hill have been known for years.
"Another damming OICS report is not going to fix the dire situation at Banksia Hill, which results in the countries' most disadvantaged and vulnerable children coming out worse than they went in," she said.
"The conflation of adult and youth justice, and the failure to implement recommendations year-on-year by successive WA governments, renders Banksia Hill totally unfit for purpose.
"Locking them in their cells all day for weeks at a time, and denying them access to education... almost guarantees their institutionalisation into adulthood."
Earlier this month the WA government announced it would invest $25.1 million towards improving services for youth in detention as part of the 2022-23 State Budget.
That included a new $7.5 million Crisis Care Unit at Banksia Hill and $3.6 million towards staffing an Aboriginal Services Unit to provide cultural support and services to help address overrepresentation of Aboriginal youth at the detention centre.
South Metropolitan MLC Brad Pettitt said Banksia Hill was a Don Dale disaster waiting to happen.
"It should not require multiple suicide attempts for kids to be given the basic supports they are entitled to," he said.
"The human rights violations occurring at Banksia Hill are not going to be fixed by chucking a bit of money at it."
"WA needs to fundamentally reform our youth justice system and that starts with raising the age of criminal responsibility to 14."
Mr Pettitt said WA needed better independent police and prison oversight and investment in First Nations-led programs to support at-risk children in their communities.