There have been at least three attempted suicides by children being held at Casuarina maximum security adult prison, it was revealed in parliament on Thursday.

In addition, almost 40 self-harm incidents and one attempted suicide were reported in just one month, July, in Western Australia's only permanent juvenile detention centre.

In parliament on Thursday Greens MP Brad Pettitt asked the State Government for information about self-harm and suicide attempts in Banksia Hill Detention Centre and Unit 18 at Casuarina adult prison, the stand-alone unit at which detainees as young as 14 are being held.

A representative for Corrective Services Minister Bill Johnston revealed between July 20 and August 8, there had been 13 self-harm incidents and three attempted suicides at Unit 18. Parliament also heard July had seen 36 self-harm incidents and one attempted suicide in Banksia Hill, and an additional three self-harm incidents in the first week of August.

Dr Pettitt said the figures proved detainees were not getting the support they needed.

"It does look like there is a lack of proper care and rehabilitation," he said.

"They said this would make the situation better, the evidence is it has made it worse."

Megan Krakouer, a member of the government's prison suicide taskforce, said the detained children were crying out for help and the danger to them was escalating.

"There was one young man, Jomen Blanket, who had nine self-harm attempts (in Acacia adult prison). His family were not notified, and on the 10th time, he passed away," she said.

"They are saying these are incidents of minor self-harm, but in the case of Mr Blanket it eventually led to his death.

"What are their credentials and expertise to determine something is minor rather than serious?

"It is a catastrophe - sending the children there (to Casuarina) was a mistake."

Ms Krakouer said advocates were deeply concerned a punitive approach was being preferred over a focus on restorative justice.

"This flies in the face of the minister saying this was the best option at this point in time. It has done nothing but cause more stress and more distress," she said.

"Their human rights are being violated and consequently you see these staggering statistics. "I am fearful that a child will take their own life for the first time in a Western Australian prison."

Ms Krakouer urged the state government to intervene and ensure appropriate measures are in place to turn the situation around.

"There needs to be an overhaul of the criminal justice system. We need to change lives and save lives," she said. "Get people from the community known to the families and the young people in there, supporting them, and they will bring some peace and stability.

"This is causing a lot of angst in our community. Bill Johnston was warned but the warnings fell on deaf ears, of an uncaring government."

Commissioner for Corrective Services Mike Reynolds said any instance of self-harm in department facilities is concerning.

"Whether there is one, or multiple, we take any threat of self-harm or self-harm incidents extremely seriously and respond immediately with a range of specialist support services," he said.

"The group of detainees moved to Unit 18 were relocated because of the significant risk they posed both to themselves and others while at Banksia Hill.

These behaviours have persisted during their transition however stability is increasing at the temporary facility and at-risk behaviours are decreasing.

"The detainees at Unit 18 have the opportunity to receive one-on-one care and support from a dedicated team of experienced psychologists, youth support officers, mental health workers, program staff, teachers and mentors to help them modify their behaviours."

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