Maitland-Newcastle Bishop Bill Wright acknowledged that Brennan’s sexual abuse of a teenage Mr Miller in 1978 was “deliberate and premeditated and Brennan used the authority of his role as Rector to do it”.

Although Brennan was charged with sexually abusing two other former students when he died in 2012 it is the first time a church representative has formally confirmed Brennan as a child sex offender.

Bishop Wright’s acknowledgement appeared in a letter on September 14 after the diocese settled a significant compensation claim brought by Mr Miller, a barrister who wrote the 2016 book The Priests. In the book he argued the Catholic Church’s mandatory celibacy rule is the core issue for the church to address in the wake of the global child sexual abuse tragedy.

In its final report in 2017 the Royal Commission into Institutional Responses to Child Sexual Abuse recommended voluntary celibacy for clergy after finding mandatory celibacy contributed to a “culture of secrecy and hypocrisy” in the church that led clergy to lead double lives.

In his apology letter Bishop Wright said Mr Miller revealed “confronting and terrible truths” about Brennan’s offending. 

“As a Catholic priest I feel great shame that Tom Brennan, an ordained priest of the Diocese, chose to inflict his sexual desires upon you,” Bishop Wright wrote.

“Brennan and all those who harmed children fundamentally betrayed their vocation. I am sorry.”

Brennan was principal of St Pius during its darkest period between 1973 and 1983, when possibly 100 students were sexually abused by teachers, including Brennan who was charged shortly before his death in 2012 with sexually assaulting two former students.

The one-time acting Maitland-Newcastle bishop, described by former bishop Michael Malone as his “right-hand man”, was the first Catholic cleric in Australia to be convicted of concealing another priest’s offences in 2009, and one of only a handful in the world.

Brennan was convicted of making a false statement to police in which he said he had received no allegations about the priest, who cannot be named for legal reasons.

A subsequent trial included evidence that Brennan received multiple reports of the priest’s offending.

Mr Miller said the letter was “quite an acknowledgement” and he appreciated the bishop’s sincere and genuine words, and particularly his recognition of the great pain his parents experienced because of the abuse.

“I understand that your parents brought you to St Pius X College, Adamstown to receive a safe and disciplined education and that Rev. Tom Brennan as Rector of the college promised you would receive that,” Bishop Wright wrote.

“As a man who has committed his life to the church, I feel great regret that you and your parents were betrayed.”

Mr Miller said the apology letter was important because it was the diocese confirming Brennan sexually abused him, for “any people out there who, I imagine, might say it didn’t happen”.

“The apology letter was the last piece of the puzzle of holding the church accountable. I’ve got to give the bishop a pretty high score on how he handled it.”

Mr Miller was scathing of the Australian Catholic Bishops Conference response to the royal commission recommendation on voluntary celibacy. The bishops raised the recommendation with the Vatican but said mandatory celibacy was a “long-established and positive practice of the church”. The National Council of Priests last week supported optional celibacy and married priests.

The bishops’ response was “misleading, disingenuous and disgraceful” and failed to acknowledge the royal commission’s conclusion that evidence suggested mandatory celibacy was an “unattainable ideal” for many priests, leading to serious consequences, Mr Miller said.

The bishops’ response to the celibacy recommendation was “another example of the bishops playing a little game of semantics” on an issue that is “absolutely at the core of why the church’s responses to child sexual abuse was so catastrophic”, he said.