Just five inmates are being held at a $17 million prison work camp that costs almost $1.4 million a year to run.
As the prison system grapples with overcrowding and the State Government tries to rein in costs, the Warburton prison work camp sits almost empty.
Built three years ago, it is designed to hold 24 prisoners.
It is one of four WA work camps - which put minimum-security prisoners to work in regional communities - none of which is fully occupied.
The use of work camps, considered a way to help prisoner rehabilitation and reduce reoffending, has expanded dramatically under the Barnett Government.
It is building a fifth, $14 million camp near Roebourne, which will open this year, hold 30 prisoners and cost an estimated $3.2 million a year to run.
The State's total prison population reached 5138 last week and prison officers warn of the problems linked to chronic overcrowding and staffing shortages.
Up to 20 prisoners rioted at Albany Regional Prison, which has a design capacity of 186 and now holds 303 prisoners, on Thursday, smashing up cells. The inmates barricaded themselves in a maximum-security unit for more than eight hours before surrendering.
When asked why more prisoners were not being sent to work camps, the Department of Corrective Services said community safety was paramount.
"Only offenders who have been assessed as suitable to be transferred to a work camp will be stationed in one," it said.
"Decisions are based on a balance between safety of the community and the rehabilitation needs of the offender."
Latest Government figures reveal eight fly-in, fly out prison officers supervise the five prisoners at Warburton work camp.
Twenty inmates were being held at Wyndham prison work camp at April 10, below its capacity of 30, at a cost of more than $2.5 million a year.
The Walpole prison work camp, which has a capacity of 12 and costs $537,730 a year to run, had eight inmates. The Wheatbelt camp was holding 16 prisoners, under its capacity of 20, and costs $903,823 a year to run.
WA Prison Officers Union secretary John Welch said it was worrying that work camps were under-used while there was overcrowding in other prisons. "We need to ensure we have sufficient prisoners to fill them, just as we need to ensure there are appropriate resources for metropolitan and regional prisons," he said.
Shadow corrective services minister Paul Papalia said many prisoners were suitable to serve sentences at work camps. "That's an extraordinary wasteful situation in light of the massive overcrowding in metropolitan and regional prisons," he said.
"It demonstrates complete mismanagement by the Barnett Government."
Corrective Services Minister Joe Francis declined to comment.