Tensions have reached "breaking point" at Western Australia's Hakea Prison as a gang culture develops, putting inmates and prison officers at the "overcrowded and underfunded" facility in danger, according to the WA Prison Officers' Union (WAPOU).

Key points: WA Police have investigated three deaths at the Hakea remand prison this year

WA Police have investigated three deaths at the Hakea remand prison this year The Prison Officers' Union said tensions have reached "breaking point" and could risk lives

The Prison Officers' Union said tensions have reached "breaking point" and could risk lives The inspector of custodial services said living standards were not decent or humane

The concerns come after WA Police launched investigations into three separate deaths at the prison this year, including an inmate who died in hospital on Wednesday.

The Department of Justice confirmed the death of the 65-year-old man, who was taken off life support after allegedly being assaulted by another prisoner in the exercise yard at the prison two weeks before.

In March, a 26-year-old man was found dead in his cell, prompting investigations into the circumstances around his death.

Meanwhile, homicide detectives have charged six men in relation to death of Alf Eades, who was allegedly attacked in his cell at Hakea in February.

The 46-year-old remand prisoner died in hospital after he sustained spinal injuries and swelling to the brain in the attack.

Six men have been charged in relation to the death of Alf Eades at Hakea in February. ( ABC News: Louise Merrillees )

Mr Eades' cousin and the chairman of the Deaths in Custody Watch Committee, Mervyn Eades, said Alf had raised concerns about gangs running the prison.

"A phone call that came out of Hakea prison was that Alf did not feel safe and comfortable where he was, complaining of needing to be removed from where he was because he felt threatened to be there," Mervyn Eades said.

He said his cousin suffered schizophrenia, a serious mental illness, and should not have been placed in the prison system during his remand.

"No one with mental health impairments — and there are many, many that are in prisons — should not be in that sort of environment."

Corrective Services Commissioner Tony Hassall said the prison system was challenged because over 10 per cent of prisoners had a serious psychiatric condition.

"We have a full suite of care professionals at Hakea that do a great job," he told ABC Radio Perth.

"Nurses, doctors, psychologists, providing a range of services to prisoners.

"But the question is — is prison the right place for some of these people?

"I don't think it is."

'Gang culture developing': union

The WAPOU said it was clear Hakea prison was struggling to handle overcrowding.

"The conditions there are far worse than they've ever been in the past," state secretary Andy Smith said.

The WAPOU says the situation is at crisis point. ( ABC News )

"It's crisis point. We have a department and a government that inherited a system that was just depleted."

He admitted there was a gang culture developing at the prison.

"Offenders who are in the same gangs are ending up in the same prisons, so the same gang culture that you have on the outside is developing on the inside," Mr Smith said.

"Without the number of officers, without the supervision, it is extremely difficult, if not impossible to control that."

The inspector of custodial services, Neil Morgan, tabled a damning report in WA Parliament in April that claimed overcrowding meant the living standards at the prison were not decent or humane.

"It is an aged prison, and most of it is too small and no longer fit for purpose," Mr Morgan said in a statement.

Neil Morgan says Hakea Prison is severely overcrowded. ( ABC News: Briana Shepherd )

"It is also severely overcrowded, with no signs of reprieve.

"In 2015 it held 900 people in 12 residential units. Remarkably, at the time of this inspection it held almost 1,200 men in just 10 units."

He noted the increase in prisoner-on-prisoner assaults since last year was in correlation with the depleting physical and human resources at Hakea.

"The crowded conditions make it extremely difficult for the prison to manage the different prisoner cohorts, and the forced doubling up of single cells adds to the risks."

Mandatory rehabilitation could help offenders

Murray Kinnane said his son started using various drugs when he was 14, later moving onto methamphetamine, and had been involved with the police ever since.

Now aged 20, his son was in Hakea prison on remand, Mr Kinnane said, and he was concerned for his welfare.

"Yes, he is vulnerable, because as an addict they end up just partnering up with some of the more high-risk offenders that have done some awful things," Mr Kinnane said.

Murray Kinnane says he is concerned for the welfare of his son, who is on remand at Hakea. ( Supplied: Murray Kinnane )

He said the overcrowding at Hakea could be combatted by imposing mandatory rehabilitation.

"There's a lot of people just sort of sitting there waiting for their trials when most of those should really be in some sort of rehabilitation," he said.

"This is not working."

When asked about the recent deaths at Hakea, Corrective Services Minister Fran Logan said they were a "tragic coincidence".

"As these matters will be investigated by the police and coroner, it would be inappropriate to comment further," Mr Logan said.

He said provisions were being made control violence within the prison.

"Hakea prison has implemented a tighter management and security regime around disruptive and violent prisoners, which includes moving them to other prisons throughout WA," Mr Logan said.