Staff shortages and a toxic culture have created a volatile situation inside the centre, putting frontline workers and children at risk, several sources alleged.

"I'm looking for work. We all are," said one youth worker, describing how staff morale had finally hit rock bottom.

"Nobody is proud to work at Bimberi," a second Bimberi employee added.

"They are overworked, underpaid, understaffed, belittled and threatened."

Tensions inside the centre erupted on May 6 last year when three detainees and three staff members were involved in a violent altercation that resulted in the staff members being sent to hospital.

Four staff members were suspended following the attack, with an independent investigation yet to be finalised more than a year later.

The constant shroud of investigation and suspicion inside Bimberi created an extremely stressful working environment, a source said.

"It is a very disturbing and destructive workplace."

Another source described how a lack of training in force and restraint techniques contributed to many of the violent incidents.

"Staff were not appropriately trained to deal with force," they said.

"They had not completed training in three years."

The ACT government's executive director of youth services, Dr Mark Collis, contended that the centre followed a comprehensive training process.

"I took the option to check the other day the training audit that we do on a regular basis.

"In the last 10 months, 87 per cent of all the delegated youth workers required have had refresher training.

"There are two more scheduled refresher trainings in the next six weeks.

"Those 13 per cent who don't have training have all been through one of the most intensive induction training procedures in any youth justice centre in Australia."

It is not just frontline Bimberi staff who are concerned about the way the territory deals with young offenders.

"There is an attitude within the system that these are little criminals, and we aren't here for their welfare," said a veteran of the ACT's wider youth justice system.

"It's a tragedy. We are so small here in the ACT and should be doing so much better."

Following the May 6 assault last year, The Canberra Times understands that around 30 frontline workers held a vote of no confidence in the management of Bimberi.

"The vote was a vote of no confidence in the management team," a source said.

"100 per cent of the attendees agreed."

The CPSU's regional secretary, Brooke Muscat-Bentley, confirmed there had been a meeting where issues such as training and staffing were raised.

"Bimberi staff informally expressed their lack of confidence in management at a meeting last year, reflecting their frustration with significant issues at the centre," she said.

"The CPSU followed up with Bimberi management on members' concerns soon after that meeting and we've continued to be closely involved to improve the lines of communication and ensure a range of improvements are made."

The Community Services Directorate said it had no knowledge of the confidence vote ever being raised, but was working closely with the union to fix issues.

"I am aware the meeting happened and I am aware of the confidential information the union discussed with me around ways we could improve communication," Dr Collis said.

"What I can say is that at no point was there every relayed to me that there was ever a vote of no confidence at that meeting."

Dr Collis said a "workplace consultative committee" had recently been established to work through staff concerns raised with the union.

He also said he had no evidence to suggest there was a bullying culture inside the centre.

"What I will say again is that we have a good and transparent relationship with our staff.

"They are on a number of committees and we work closely with them.

"From time to time we get feedback from staff that things can be improved, and we improve them."