The Pope has accepted the resignation of the Bishop of Palmerston North, Charles Drennan, following an investigation into a complaint of unacceptable behaviour of a sexual nature.

Photo: Supplied / Catholic Church

The Metropolitan Archbishop of New Zealand, Cardinal John Dew, said in the eyes of the Catholic church, Bishop Drennan's behaviour was completely unacceptable.

"No doubt it is a question that will be asked by the authorities in Rome - how behaviour, which is completely unacceptable and inappropriate could be undertaken by someone in the role of a bishop," he said.

The complaint was made by a young woman and the former bishop tendered his resignation to Pope Francis.

The Pope's decision was announced by the Vatican at 11pm on Friday NZ time.

Bishop Drennan is also leaving his role with the Royal Commission into historic abuse. He stepped aside from the role several weeks ago.

Charles Drennan was the only high ranking clergyman on the group managing co-operation between the Catholic Church and the Royal Commission.

Cardinal Dew said he would take his place and work with the Royal Commission.

In a news release last night, Cardinal Dew said upon receiving the complaint the New Zealand Church's independent investigation body, the National Office of Professional Standards (NOPS), brought in an independent, licensed investigator under his oversight.

The cardinal said Bishop Drennan stood aside from his duties and both he and the young woman participated in the investigation.

The young woman has been informed of his resignation and the Church is in ongoing contact with her, Cardinal Dew said.

The Church was committed to giving continuing support to the young woman, her family and those around her.

"The young woman has requested that details of the complaint remain private," Cardinal Dew said.

"In the eyes of the Catholic Church, Bishop Drennan's behaviour was completely unacceptable, and it fully supports the young woman for coming forward to NOPS."

The clergy, staff and church leadership of the Diocese of Palmerston North had been told of the acceptance of the resignation and provided with guidance and resources to help them to support parishioners and other members of the Catholic community. The wider Church of New Zealand would also be advised and supported.

"The Catholic Church has no tolerance for any inappropriate behaviour by any of its members. I encourage anyone who experiences such behaviour to bring it to the attention of the Church, police or any organisation with which they feel comfortable," said Cardinal Dew.

Earlier complaint

Bishop Drennan had been the subject of a complaint in the past.

The details of the complaint haven't been disclosed but the Catholic Church said it wasn't a sexual assault.

Cardinal Dew said another woman had spoken to him about that, but had not wanted to meet independent investigators.

Church's response significant

Professor emeritus Peter Lineham said the Catholic Church had a history of covering up similar allegations which made its response to this incident precedent setting.

He said it suggested that the church had realised it had to change.

"That this is the very issue which has been at the heart of concerns that the church is often not addressing things clearly or explicitly and thus offenders have got away with things or repeat offences.

"I think Cardinal Dew has been absolutely on the mark in the way he has very firmly ensured that the girl's privacy is protected, but she's offered support."

Christchurch role before a move to Palmerston North

According to the Catholic Church's website, Bishop Drennan worked for seven years for the Vatican's Secretariat of State under St John Paul II and Pope Benedict XVI.

He was appointed co-adjutor Bishop of Palmerston North on 22 February, 2011.

This was the same day as a devastating earthquake struck Christchurch, where he was based, being administrator of the Cathedral of the Blessed Sacrament, which suffered severe damage.

He was ordained bishop on 11 June, 2011 and was installed as Bishop of Palmerston North in 2012.