Under-fire security company Serco has launched an immediate investigation after a prisoner was left unguarded by its staff during a trip to Royal Perth Hospital.
A Serco officer has been suspended after the incident came to light following complaints from hospital staff last weekend.
It is believed the prisoner was left alone as one of his guards went to the toilet and the other also left, uncomfortable being on his own with the shackled inmate.
A statement from Serco confirmed senior management gave "corrective instructions" by telephone and then attended the hospital in person to review the incident and meet hospital staff.
"The matter is currently the subject of an investigation. A member of staff has been suspended, pending the outcome of the investigation," the statement said.
The company said it was a "clear expectation" that officers should be positioned in the room with the prisoner when carrying out a hospital sit.
"At least two officers are assigned to each hospital sit, which allows for each of them to take comfort and refreshment breaks while the other remains with the prisoner," the statement said.
"If an officer fails to follow procedure, they will be subject to the disciplinary process, with outcomes up to and including dismissal."
The incident is the latest in a recent list of incidents involving Serco, which include four escapes from an immigration detention centre near Northam, and two escapes of prisoners - one a violent rapist.