Senior staff at a Catholic school in Tasmania, including the then principal and his boss, were aware of allegations a teacher was sexually abusing multiple children as far back as 1971, and sought to move the teacher to a different parish, a letter obtained by the ABC reveals.

Key points: Greg Ferguson left Marist College in 1972 and worked across Australia for several decades

Greg Ferguson left Marist College in 1972 and worked across Australia for several decades Father Hosie's letter reveals concerns abuse by Ferguson could become a court case

Father Hosie's letter reveals concerns abuse by Ferguson could become a court case A former student said he saw Ferguson chasing students while naked

Greg Ferguson as pictured in the 1971 Marist yearbook. ( Supplied: Marist Yearbook 1971 )

The teacher, Greg Ferguson, was convicted of historical child sex offences against two students in 2007 relating to his time at Burnie's Marist College in the early 1970s.

A letter written by then Marist College principal, Father Bernard Hosie, to his boss Marist provincial Peter Guiren in November 1971 sought advice on whether Ferguson should be moved on after reports he was "fooling around" with young boys at the school.

"I have reports of about 8 boys that Greg Ferguson (they claim) has been fooling around with in his room ... it would ... be very easy to move him if it had to be done overnight," the letter states.

"I think the best thing is to sit out the year and leave Greg here. But the affair is pretty widely known among the boys I fear," it goes on to say.

Ferguson left Marist College in 1972 and worked across Australia over several decades, including in Gladstone in Queensland.

A source within the Catholic Church has confirmed with the ABC that the letter is genuine.

'We are sitting on a volcano'

The letter reveals concerns by Father Hosie that the abuse of children by Ferguson could become a court case, and that he shared his concerns with at least two other staff.

"I am, of course, frightened of a court case. It would need only one parent to lay charges," the letter said.

"We are sitting on a volcano, and it is not very pleasant."

The letter is signed with a "received by" mark and the signature of Father Guiren, who was principal of the college before Father Hosie.

Multiple allegations of sexual abuse surround Father Guiren during his time as principal and were made public for the first time in an ABC investigation earlier this year.

Including Ferguson, five former staff associated with the college have been sent to prison on child sex offences.

They include Thomas Fulcher, who was sentenced to four years' prison, two without parole, in December 2018 after pleading guilty to sexually abusing two boys at Marist College between 1964 and 1967.

Father Hosie's letter refers to Fulcher, who was part of the teaching staff at the time.

"Strange that Tom Fulcher caught nothing of it though," Father Hosie questions in the letter.

Father Hosie later left the Marist Fathers and died in the United States in 2016.

'He pinned me against the wall'

Andrew Murray says he witnessed Ferguson chasing boys around naked. ( ABC News: Henry Zwartz )

One former student, Andrew Murray, told the ABC he had been told to go to Ferguson's room one night in November 1971, and when he arrived, witnessed the teacher naked chasing sixth graders around his room.

Father Bernard Hosie died in the US in 2016. ( Supplied: Marist Yearbook 1971 )

"I knocked on the door, the door opened, and I was confronted with three young students, they would have been sixth grade, being chased around a room by Father Greg Ferguson," Mr Murray said.

"He was erect, he had no underpants on."

Mr Murray, who was 16 at the time, said he took the children back to their rooms that night before reporting it to Father Hosie the next day.

"When I told Hosie he pinned me against the wall, holding me by the shirt collar of the throat and in turn told me if I ever repeated such vile accusations about Father Ferguson again I would be leaving school without my end of year results; he then told me to get out," he said.

Another former student, who did not wish to be identified, said he recalled a similar incident that on the same night.

"We were scared to go to his [Ferguson's] room. When we got there ... he was naked," the student said.

"It was horrible."

Mr Murray said it was common knowledge among students to avoid Ferguson's room.

"He had the nickname, 'Mr Date', we tried to avoid going there unless we were in pairs," Mr Murray said.

Burnie 'Tasmania's Ballarat'

Five staff members associated with Marist College have been convicted over sex offences, they are: Stephen Grant Randell, found guilty in 1999 on 15 charges of indecent assault against nine girls between 1981-1982

Stephen Grant Randell, found guilty in 1999 on 15 charges of indecent assault against nine girls between 1981-1982 Paul Ronald Goldsmith, jailed for more than six years in 2005 on 42 sex offences against 20 boys aged between 13-16. He died in Tanzania in 2016

Paul Ronald Goldsmith, jailed for more than six years in 2005 on 42 sex offences against 20 boys aged between 13-16. He died in Tanzania in 2016 Gregory Laurence Ferguson, who taught at the college in the 1970s, sentenced to five years' prison in 2007 after two separate convictions

Gregory Laurence Ferguson, who taught at the college in the 1970s, sentenced to five years' prison in 2007 after two separate convictions Roger Michael Bellemore sentenced to four years' prison in 2008 after being convicted of assaulting three students between 1966 and 1971

Roger Michael Bellemore sentenced to four years' prison in 2008 after being convicted of assaulting three students between 1966 and 1971 Thomas Fulcher, sentenced to four years' prison in December 2018, two without parole, after admitting to sexually abusing two former students

Two former students have told the ABC they believe they are part of the group of eight mentioned in the letter, and allege they were sexually abused by Ferguson in the early 1970s.

They said they had raised their experiences of sexual abuse with school staff.

Former Tasmanian Member of Parliament and sex abuse survivor Paul O'Halloran told the ABC the scale of abuse in the community was "Tasmania's Ballarat".

"Burnie is at the centre of a horrific scale of sexual abuse going over several decades, right through from the 60s to the 80s," Mr O'Halloran said.

"There needs to be a real investigation, a close look at what happened."

Mr O'Halloran, a former student at the College, was sexually abused during his education there and successfully lobbied for the Royal Commission to visit Tasmania as part of its hearings into historical sex abuse cases.

Paul O'Halloran says Burnie is at the centre of an "horrific scale of sexual abuse". ( ABC News: Henry Zwartz. )

In a statement, the Marist Fathers said "the response indicated by the letter was totally inappropriate and inadequate".

"If repeated today, it would also be against the Marist Fathers' current policy, against the law, and contrary to mandatory reporting obligations," the statement read.

"In general, awareness of responsibility to report, and a lack of awareness of the terrible harm inflicted by sexual abuse, were totally lacking.

"The Marist Fathers are not aware of any further historical records or documents indicating that staff were acting inappropriately with children.

"We cannot and will not attempt to contest the idea that the approach taken in the past in a number of situations was inappropriate and we will continue to take a survivor-focussed approach to anyone coming forward."

In a statement, the Archdiocese of Hobart said "the historical act of moving priests suspected of child sexual abuse between parishes or schools is reprehensible".

"The Archdiocese of Hobart has implemented the Safe Communities Policy and Framework that goes beyond meeting its legal obligations. The policy and framework ensures the reporting of all disclosures, allegations, incidents or concerns in relation to abuse," it said.