Greens leader Cassy O'Connor on Thursday said it was understood the same staff member, who was alleged to have raped a teenager, was known to have masturbated in front of detainees at the centre.

Ms O'Connor asked Human Services Minister Roger Jaensch why it had taken management from January to November last year for the worker to be stood down.

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She later asked Mr Jaensch to confirm if an incident had occurred in August 2019 where two detainees discussed sexually assaulting another younger detainee.

"We understand the Serious Event Review Team was alerted, as was Child Safety Services," Ms O'Connor said.

She asked if both cases had been referred to Tasmania Police for investigation.

Mr Jaensch accused Ms O'Connor of being selective on sharing issues brought to her regarding the detention centre with the government.

"I hope she has provided information as soon as she has been in possession of it because we take these cases very seriously and we want to investigate them thoroughly," he said.

"Sadly, in Tasmania we will always need a youth detention facility.

"As long as courts are sentencing that very small number of young people who commit crimes to custodial terms, we will need a facility that can receive them."

Mr Jaensch later said one matter had been referred to police and was subject to an internal review.

He said the other matter was subject to ongoing investigation.

After Question Time, Ms O'Connor sought to move an urgent motion for the House of Assembly to acknowledge the detention centre was an unsafe place for young people and that it had long failed detainees.

The motion called for the government to establish therapeutic alternatives to Ashley and implement interim measures, including independent oversight, until it was closed.

"For nearly 100 years, Ashley has been a house of horrors for children and young people who end up in there," Ms Connor said.

"There has been a culture of abuse and cover-up at Ashley Youth Detention Centre."

She said a 2016 independent report noted the detention centre cost $9 million a year to run and house between six to 13 children.

One of its recommendations from report authors Noetic Group was that it should close.

"The independent expert advice was that hellhole should close and that therapeutic alternatives should be established," Ms O'Connor said.

Labor's David O'Byrne said the party was open to suspending daily business to debate the Greens' motion.

Leader of Government Business Michael Ferguson said the bill could have been debated in private members time on Wednesday.

The Liberals opposed suspending government business to allow for a debate to occur.