The death of an Indigenous teenager from a self-inflicted injury has prompted Western Australia's government to close a youth detention facility.
Premier Roger Cook says a new facility to replace Unit 18 at Casuarina Prison will be built alongside Perth's Banksia Hill juvenile detention centre.
"Unit 18 will eventually close in a safe and sensible manner, which is what I've long been saying I want to see happen," he told reporters on Thursday.
"The new facility will be specifically designed to meet high security and therapeutic needs of detainees who are complex, challenging and often dangerous."
A recently completed youth justice infrastructure review found Banksia Hill could not safely and securely accommodate the 20 or so high-risk prisoners being held at Casuarina Prison.
Mr Cook said the proposed two-site model would allow challenging youths being held in Unit 18 to be provided with high levels of support.
A plan and business case is yet to be developed for the new facility and there is no scheduled opening date.
"Everyone wants to see the closure of Unit 18 ... (but) I want to be clear that while the new facility will allow us to shut Unit 18, it won't happen overnight," Mr Cook said.
Unit 18 custodial officers discovered 16-year-old Cleveland Dodd unresponsive in his cell in the early hours of October 12.
He was taken to hospital in a critical condition, where he later died, causing outrage and grief in the community.
Mr Cook said $77.1 million had been budgeted to improve staffing, facilities and services in WA's youth justice system.
This includes $34.2 million to boost staffing levels at Banksia Hill and Unit 18 and $8.2 million to fund upgrades to programs and services such as Aboriginal health and fetal alcohol syndrome disorder training.
He said the troubled Banksia Hill facility had dramatically improved since a riot in May caused about $30 million damage.
The amount of time detainees spend outside their cells has increased to about nine hours per day and assaults on staff have dropped to 39 per cent, with critical incidents falling to 21 per cent compared to the first half of the year.
"We've achieved this by making Banksia Hill safe, enabling the facility to return to normal conditions, something that we have not seen for a number of years," he said.
Opposition spokesman for corrective services Peter Collier said the culture within the youth justice system needed to improve to ensure the safety of detainees.
He questioned why it had taken so long for the government to take action over Unit 18 and said more detail was needed.
"While Unit 18 remains open it is a scourge on the reputation of (the state)," he said.
The Justice Reform Initiative said the youth justice system needed an overhaul and urged the government to review its intervention strategies for children and young people before building the new facility.
"A new building is not the same as a new approach," executive director Mindy Sotiri said.
The problems at Banksia Hill have been clear for decades, she said, and the pledge for a new maximum security facility next door "does not address the over-use of harmful incarceration" of children there.
The union for custodial officers, The Community and Public Sector Union/Civil Service Association, described the pledge to build a new detention facility and funding boost as a potential reset for youth justice in WA.
But it said a timeline for the project was needed.
13YARN 13 92 76
Aboriginal Counselling Services 0410 539 905
Lifeline 13 11 14
beyondblue 1300 22 4636
Australian Associated Press