Upon receiving the complaint, the New Zealand Church's independent investigation body, the National Office of Professional Standards (NOPS), contracted an independent, licensed investigator to undertake an investigation under the oversight of Cardinal Dew.
Bishop Drennan stood aside from his duties and both Bishop Drennan and the
young woman participated in the independent investigation.
The young woman has been informed of his resignation and the church is in ongoing contact with her, the New Zealand Catholic Bishops Conference said in a statement.
"The young woman has requested that details of the complaint remain private," Cardinal Dew said.
"It can be confirmed that Pope Francis has accepted the resignation. 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 have been told of the acceptance of Bishop Drennan's resignation and provided with guidance and resources to help them to support parishioners and other members of the Catholic community.
Cardinal John Dew said the wider Church of New Zealand will 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."
- AP