Former Mental Health Commissioner Tim Marney will not continue in his role leading reforms of Western Australia's trouble youth justice system, with his contract not renewed after six months in the position.

In April, Mr Marney was tasked with put into effect a new model of care for children at Banksia Hill Detention Centre.

At the time, the WA government said Mr Marney joined the state's Department of Justice to execute a "comprehensive change management plan" at Banksia Hill aimed at giving detainees "the care and services they need".

While working at management consultancy Nous Group, Mr Marney had led the development of a new operating philosophy and service model to guide how Banksia Hill functions.

On Monday it was announced the man former corrective services minister Bill Johnston described as being "ideally suited" to addressing the problems in Banksia Hill would not have his contract renewed by the state government.

Indigenous youth are radically overrepresented in Western Australia detention system. Critics have cited a range of problems in the system, including a shortage of qualified staff, a lack of culturally appropriate care, and the use of lockdowns.

Banksia Hill and the stand-alone youth facility at Casuarina Prison, Unit 18, have been plagued by disturbances over a long period, as well as the use of lockdowns or solitary confinement of youth for prolonged periods – which was found to be unlawful by the Supreme Court in September last year.

Inspector of Custodial Services Eamon Ryan, who has been a fierce critic of Banksia Hill, told National Indigenous Times that for more than 10 years his office has "advocated strongly for a trauma informed operational philosophy at Banksia Hill".

"In April 2023 we welcomed the appointment by the Department of Justice of a consultancy group, led by Mr Tim Marney, to develop an Operational Philosophy and Service Model for juvenile detention," he said.

"Once the initial model was developed, the appointment of someone with Mr Marney's expertise, background, and experience to lead the implementation of the model of care was a was a significant step forward.

"We have previously acknowledged that leading the implementation of these reforms was always going to be very difficult and challenging, but Mr Marney's expertise and detailed knowledge of the proposed new model of care would be a significant benefit to him in leading this assignment. We, like so many other stakeholders, were optimistic that the implementation of these reforms would proceed, and the significant reforms given every chance at success.

"I was surprised, and somewhat disappointed, to hear that Mr Marney would not be continuing to lead this important reform in juvenile detention."

Mr Ryan said he hoped "the reform agenda around implementing the new model of care does not stall", and that "the Department appoints someone with the required skills and expertise to continue the work started by Mr Marney".

"I have requested a detailed briefing from the Department about plans for the future of Banksia Hill, including plans to continue the implementation of the new model of care," he said.

Longtime Indigenous youth justice advocate Megan Krakouer told National Indigenous Times that appointment had been "misguided".

"(They) hired a former long-serving bureaucrat to do… restorative work in the lives of the most troubled children," she said.

"I am disappointed not just in Roger Cook and Paul Papalia… I am also disappointed in Brad Pettitt and Peter Collier claiming Tim Marney needed more time. If you cannot get something working straight up, well it won't work ever."

Ms Krakouer said her National Suicide Prevention & Trauma Recovery Project, Gerry Georgatos, had demonstrated the model needed in youth justice in a two-month period.

"Gerry Georgatos… had only eight weeks to work in Banksia in March to May 2020… he more than halved the female prisoner population in Banksia and deescalated every potential incident he came across. Gerry got the model right from day one," she said.

"The pollies need to mature and listen to the real and proven experts, such as Gerry, and get him to craft what works and to assist in developing the layered supports and workforces so desperately needed."

Data provided to the Western Australian parliament shows that since the start of May the amount of time Banksia Hill detainees have spent confined to their cells has fallen significantly, however detainees at Unit 18 continue to little more than two hours out of their cell per day.