The Department of Corrections is facing a backlash after introducing random drug and alcohol testing for prison guards.
The new testing regime took effect on July 1 and means any officers involved in accidents or fights - or who are suspected of being under the influence - will have to undergo on-the-spot testing.
The Corrections Association union estimates 2000 guards will be tested each year, at a cost of more than $1 million.
President Beven Hanlon said it was ludicrous for guards to be tested when drugs were rife among the prisoners, who can be tested only if they volunteer.