Jason has been in and out of Western Australia's prison system for 15 years and says he has never seen conditions so bad.

Key points: A former inmate describes conditions inside the prison system as a "ticking time bomb", with staff and prisoners under increasing stress

A former inmate describes conditions inside the prison system as a "ticking time bomb", with staff and prisoners under increasing stress Unions are concerned staff recruitment is not keeping up with the state's rising prison population

Unions are concerned staff recruitment is not keeping up with the state's rising prison population The Government says its training academy has "never been so busy" with a campaign to attract 458 new prison officers

He was recently released from Bunbury Regional Prison in the state's south-west after serving 18 months across maximum, medium, and minimum-security units.

Jason — who's name has been changed to protect his victims — said a recent 160-bed expansion of the prison had done little to relieve pressure on inmates and staff.

"You could tell the guards were stressed," he said.

"They brought heaps of new staff in, but a lot are quitting because they just can't handle the pressure … they're not properly equipped."

'A ticking time bomb'

Jason also served time at Perth's Hakea Prison during his most recent sentence.

He said he was forced to sleep on floors next to toilets, was regularly locked in his cell for up to 23 hours a day, and witnessed an increase in violent behaviour among frustrated inmates.

The inquest found counselling service staffing levels had dwindled despite a rise in prisoner numbers. ( ABC News: Louise Merrillees )

"Hakea is just constant lockdowns now because they say they're short-staffed," he said.

"Prisoners are locked in a little cubicle … it's just a ticking time bomb.

"If you treat people like animals, they're going to act like animals."

According to the WA Prison Officers Union (WAPOU), the inmate muster at Hakea sat around 1,167 on Friday and was likely to tip over 1,200 across the weekend.

The union said state-wide prisoner numbers had also reached a record 7,149 across all 17 detention facilities.

WAPOU secretary Andy Smith said conditions at Hakea were "unsafe" and there was "a genuine risk of further major incidents", if the population remained at 1,200 for an extended period.

A 2018 report by the Inspector of Custodial Services (OICS) found the prison was "severely crowded with no signs of reprieve".

Andy Smith says prison officers are working in an increasingly volatile environment. ( Supplied: WAPOU )

Mr Smith said conditions had not improved since the findings were released.

"Conditions at Hakea are overcrowded, stressful and degrading, and it has only grown worse.

"Unfortunately, we were promised relief with new units at Casuarina Prison, but they have now been delayed until at least May.

"This will not come soon enough for our members, who are dealing with a record prison muster."

More staff needed

Mr Smith said the Government and Department of Justice had imposed overtime restrictions on staff.

"That limits the number of positions that are filled in all prisons across the state, leaving the prisons undermanned and ill-equipped to provide the services required to maintain a safe environment for prison officers and the community," he said.

"The staff shortages exist due to inaccurate accounting over decades.

The union says new units at the prison in Kalgoorlie sit empty. ( ABC News: Rhiannon Shine )

"Our members do not want to work overtime, but without working to cover those vacant shifts, their colleagues work in a far more dangerous and volatile environment."

Mr Smith also said two units at the Eastern Goldfields Regional Prison (EGRP) in Kalgoorlie remained closed due to the department's "inaction to attract and retain staff".

"The fact that our members at Hakea are working in the conditions described in the OICS, while brand new units sit empty at EGRP, is entirely unacceptable.

"WAPOU is aware the department is recruiting more prison officers, but they are needed to cover existing shortfalls and to keep up with the ever-increasing prisoner population."

Extra pressure was also on state-wide staff numbers, Mr Smith said, because a "significant number" from the Greenough Regional Prison in the state's Midwest were still on leave following the July 2018 breakout and riots.

The Government says it plans to train another 308 officers this year. (File photo) ( ABC Goldfields-Esperance: Jarrod Lucas )

Training academy 'never been so busy'

In a statement, Corrections Minister Fran Logan said the Justice Department's training academy had "never been so busy" and was fully booked for the next year.

"The union is fully aware of the significant investment that the McGowan Government has made into fixing the mess left behind by the previous Liberal-National government," he said.

"We lifted the incomprehensible staff-hiring freeze that the previous government put in place, and the Department of Justice has an open-ended recruitment campaign to attract 458 new prison officers.

"Since October 2018, 288 prison officers were engaged in 2019 and there are plans to recruit and train another 308 new officers this year."

Editor's Note 3/3/2020: The name of one of the subjects of this story has been changed due to requests from some of the person's victims.