Bishop Wright confirmed the situation in a letter sent from his office today, Thursday.

In the letter, the bishop said he had been an "emergency admission to hospital" at the end of June, struggling to breathe.

"Despite very good care and treatment, the condition of my lungs has not improved and, we now know, is an illness from which I will not recover," the bishop wrote.

Although he does not mention it by name, the diocese has confirmed that Bishop Wright, who was a smoker, has lung cancer.

In today's letter, Bishop Wright says he is "physically incapable of performing public ceremonies or getting about without considerable assistance".

"I can no longer fulfil a bishop's role or duties," he wrote.

"Accordingly I have written to the Holy Father, Pope Francis, submitting my resignation as bishop.

"What happens next is, of course, entirely up to the Holy See. In the meantime, I will remain on sick leave and my place will be filled by the Vicar General and the excellent staff of the bishop's office, as has been the case these last months."

The Vicar General is the Reverend Andrew Doohan, who was appointed to the position in March 2018.

News of the bishop's resignation has spread quickly through Catholic circles, among those who have had problems with the church, as well as its supporters.

Bob O'Toole, joint founder and spokesperson of the Clergy Abused Network support group, wished the bishop all the best on behalf of the group.

He said he was personally saddened to hear of the bishop's illness.

"He is someone who has listened to the messages the church needs to hear," Mr O'Toole said.

In 2013, Bishop Wright published an "unreserved apology" on behalf of the diocese to those who had suffered at the hands of its paedophile priests, naming Denis McAlinden and James Fletcher for their "repeatedly committed acts of sexual abuse of children".

This was after the NSW special commission of inquiry that preceded the Royal Commission.

He published a more detailed apology after royal commission hearings in 2016, acknowledging the "sad and terrible history" of the diocese, especially as it related to the serial paedophile priest Vincent Ryan.

Bishop Wright suffered a heart attack in 2018.

In today's letter, Bishop Wright said that in times of hardship such as now it was the duty of a bishop to "be present with his people, to encourage and support wherever he can, to provide some point of stability in a shook-up world".

The bishop said he had been "acutely conscious that for some months" he had been "incapable of providing that episcopal service".

Bishop Wright thanked all of those who had sent "get well" messages and who had "held me in prayer".

"The sensation of a peace and tranquility of spirit that come from beyond oneself has been very palpable in some of the challenging moments," he wrote.

"May we continue to support each other in faith and love through all life's challenges," he concluded.

Bishop Wright was ordained as Maitland-Newcastle's eighth bishop in 2011, replacing Michael Malone, who had led the diocese since 1995.

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