Former child detainees at a Tasmanian detention centre said they were sexually abused by 55 former workers inside the controversial facility.

One former worker had sexually abused at least 11 children at Ashley over the course of nearly three decades.

Another staff member was described by 26 victims as using sexual violence and physical intimidation, including "hogtying" and forced masturbation, as a tool to control children.

The dates of the incidents span from recent years back to the 1970s.

Kyle*, who was 10 years old at the time of incarceration, said that the sexual abuse was perpetrated by workers on excursions.

"There'd be no signing of paperwork or nothing like you just literally get up, walk out, jump in the car and leave," he said.

"On several of these trips, I was sexually abused by staff."

Another former inmate, Mary*, was detained at the centre in her early teens.

"So within the first month of me being there, I was touched up by one of the workers and I knew it wasn't okay for him to do that," she said.

Mary says the perpetrator was given two weeks paid leave after her complaints was made, before returning to the facility where he supervised her.

Mary complained to the state's ombudsman that the behaviour of the worker made her feel uncomfortable, but she received a reply stating the matter would be dealt with internally by the detention centre.

Soon after, she was sexually assaulted again by the male detainees.

"The second time I was pretty badly assaulted and there was an incident where I was left alone with boys,' she said.

She says the sexual assaults continued on a weekly basis and she was even offered contraceptive pills by the staff at Ashley Detention Centre.

Staff at Ashley have covered up the abuse, that they have destroyed records or failed to report abuse at all.

*The names of former detainees have been changed