The Catholic Archbishop of Adelaide, Philip Wilson, is coming under increasing pressure to explain what he knew about clerical sexual abuse when he was an office-holder in the NSW diocese of Maitland-Newcastle in the late 1970s and 1980s.

Archbishop Wilson has just been re-elected as chairman of the Australian Catholic Bishops' Conference, and is widely tipped as a possible successor to the Archbishop of Sydney, Cardinal George Pell, if Cardinal Pell leaves Sydney to take up a senior post in the Vatican.

The Maitland-Newcastle diocese has become notorious as perhaps the epicentre of Catholic clerical sexual abuse in Australia. Four serious paedophile priests have been jailed since 1997. Father Vincent Ryan's crimes led to a $6 million compensation payout to victims - a record for the Catholic Church in Australia so far. Father John Denham is due to be sentenced later this month, and the compensation settlement with his victims is expected to be even larger. Yet another priest, Father David O'Hearn, is due to stand trial in the next two weeks.

Now a victim of convicted paedophile Father James Fletcher, who died in jail in 2006, says Archbishop Philip Wilson was a priest living in the bishop's house in Maitland when Fletcher was also living there in the late 1970s, and that Philip Wilson should have been aware that he was being sexually abused in Fletcher's upstairs bedroom.

Peter Gogarty says Philip Wilson regularly saw him in Fletcher's company as he was being taken upstairs to Fletcher's bedroom, and after he came back downstairs. At one point, when Bishop Leo Clarke became suspicious, Gogarty was banned from being in the bishop's house, but Fletcher continued to sneak him in the back door. Peter Gogarty says Philip Wilson should have intervened.

"Jim started sneaking me in the back door in the kitchen in the back of the house, straight past the common room where I would regularly pass Philip Wilson and then up the stairs to his bedroom," he said.

Conveniently for Jim Fletcher, Peter Gogarty was attending a school right next door to the bishop's house. He says the abuse would occur at lunch time and many afternoons after school. He says he has spoken to Archbishop Wilson over the phone in recent years about what the archbishop thought was going on.

"I asked now Archbishop Wilson what he thought was happening at the time. Did he know that Bishop Clarke had banned me from the house? His response was, no, he didn't know anything about that, and that as far as he was concerned Jim was a good bloke and he didn't think Jim was up to anything untoward," he said.

Peter Gogarty says he can't accept this explanation from Archbishop Wilson.

"I think, how could a man living in a house with another man not even be remotely curious as to why his house-mate was taking at least one boy up to his bedroom, and there may have been others."

Two weeks ago, Peter Gogarty lodged an official complaint with the NSW Police.

Today Archbishop Wilson responded to a series of questions put to him by the ABC. He has denied any knowledge that Jim Fletcher was sexually abusing Peter Gogarty in the bishop's house.

In 1978, Philip Wilson was made director of Religious Education for the Maitland-Newcastle diocese and taught at St Pius X High School, Adamstown, in Newcastle. St Pius X was the scene of horrific sexual assaults on young boys by another teacher at the school, Father John Denham. Denham is due to be sentenced this month over 135 offences on 39 victims. It is expected that the compensation settlement for Denham's victims will be even higher than that paid out to victims of Father Vincent Ryan, and that it could potentially bankrupt the diocese.

A former student of St Pius X High School from 1975 to 1979, Stephen Kilkeary was taught religion by Archbishop Wilson in 1978 when he was in Year 10. He says the atmosphere at St Pius X was violent, and that boys were frequently sexually assaulted. He says he finds it impossible to believe that Philip Wilson did not know about what was going on:

"My view would be that it would be impossible for anybody not to know, it was so rampant, so endemic. Everybody talked about it, not just at the school, even in the local community it was widely known that boys were being sexually abused at the school," said Mr Kilkeary.

Responding to questions put to him by the ABC, Archbishop Wilson has denied that he had any knowledge that Denham was assaulting boys at St Pius X while he was teaching there.

McAlinden allegations

Two weeks ago, a former principal of St Joseph's Primary School, Merriwa, west of Newcastle, accused Archbishop Wilson of being involved in covering-up the sexual assault of an eight-year-old girl by Father Denis McAlinden in 1985. At the time, Philip Wilson was secretary to then bishop of Maitland-Newcastle, Leo Clarke, and he was sent to the school to talk to parents. Former principal Mike Stanwell says Philip Wilson assured him that McAlinden would be sent away to get help. Instead McAlinden was transferred to another parish where he came into contact with other children, and later he was transferred to a remote parish in the Pilbara region of Western Australia. Over the next decade he sexually assaulted five more girls under the age of 10.

In 1995 Philip Wilson took a statement from one of these girls who recently lodged an official complaint with the NSW Police. The ABC has obtained a copy of her letter to police, which states:

"I have advice from a Senior Counsel that based on the documents which are now in the possession of the NSW Police, there are sufficient grounds to warrant an investigation by the Police.

"The purpose of this letter is to formally complain about the conduct of the people noted above, and to request on behalf of all the victims of Father Denis McAlinden that you undertake an urgent inquiry into their conduct."

NSW Police are now investigating documents which show that only days after Philip Wilson took the girl's statement in October 1995, Bishop Leo Clarke launched a secret "defrocking" process, promising Denis McAlinden in a letter that his "good name" would be protected. That letter concludes: "A speedy resolution of this whole matter will be in your own good interests as I have it on very good authority that some people are threatening seriously to take this whole matter to the police."

Bishop Leo Clarke died in 2006, the year before NSW Police established Strikeforce Georgiana to investigate sexual abuse in the Maitland-Newcastle diocese. Bishop Clarke was never interviewed about the full extent of abuse in the diocese.

In previous media statements, Archbishop Wilson has claimed he referred all complaints of abuse he received about Denis McAlinden to Bishop Clarke. But Peter Gogarty says he doesn't think that is good enough.

"I don't think passing on your responsibility to someone else resolves you of you own responsibility. I just see that as an easy opt out to say, 'It is not my problem'," he said.

Diocese cover-ups

Archbishop Wilson is not the first former vicar general of the Maitland-Newcastle diocese to be accused of a cover-up. In 1996 NSW Police wanted to charge Monsignor Patrick Cotter over his concealment of sexual assaults by Father Vincent Ryan in the early 1970s, but the NSW Director of Public Prosecutions ruled that Cotter was too old to stand trial. Cotter died in 2007.

Last year another vicar general, Father Thomas Brennan, was convicted of making a false written statement to protect Father John Denham, and placed on a 12-month good behaviour bond. He is the only person in a position of authority in the Catholic Church in Australia to be convicted for covering-up abuse.

The present bishop of Maitland-Newcastle, Michael Malone, has been warned by police for "tipping off" Father Jim Fletcher that he was under police investigation. The Ombudsman's report into the incident was highly critical of the bishop's role. Bishop Malone has since apologised to victims for his poor handling of the issue.

Peter Gogarty says he believes Archbishop Wilson's response to media queries has been inadequate.

"I would really like him to come clean and apologise for all of this, and I would like him to look people in the eye who have been hurt by all of this and say, 'I am sorry'."