Archbishop of Adelaide Philip Wilson leaves after sentencing at Newcastle local court on Tuesday. Photograph: Darren Pateman/EPA

The archbishop of Adelaide, Philip Wilson, will appeal his conviction and sentence for concealing child sexual abuse.

Wilson is the most senior Catholic official in the world to be convicted of the crime. On Tuesday, Magistrate Robert Stone in Newcastle local court sentenced the 67-year-old to 12 months’ imprisonment with a non-parole period of six months. He ordered that Wilson be assessed for home detention.

Wilson was found guilty in May of failing to report to police the abuse of two altar boys by a paedophile priest, James Fletcher, in the 1970s.

On Wednesday afternoon Wilson announced he would lodge an appeal.

“I am conscious of calls for me to resign and have taken them very
seriously,” he said in a statement.

“However, at this time, I am entitled to exercise my legal rights and to follow the due process of law. Since that process is not yet complete, I do not intend to resign at this time.

“However, if I am unsuccessful in my appeal, I will immediately offer my resignation to the Holy See.”

The archdiocese cannot remove Wilson from his role – only Pope Francis has the authority.

The prime minister and opposition leader are among those calling on him to quit.

“I am surprised that he has not resigned,” Malcolm Turnbull told reporters on Wednesday. “Clearly, given the outcome of the case, the lawsuit and prosecution, he should resign.”

Bill Shorten said the justice system had unequivocally spoken.

“Mr Wilson’s action were inexcusable and his position is untenable,” he said in a statement.

Peter Creigh and another altar boy gave evidence that they told Wilson in 1976 that Fletcher had repeatedly abused them in the New South Wales Hunter region but that Fletcher, who was then an assistant priest, had done nothing.

Creigh was 10 years old at the time. The second altar boy, who can’t be named for legal reasons, said he was about 11 when he went into the confessional box to tell Wilson that Fletcher had abused him. He said Wilson had told him he was telling lies because Fletcher “was a good bloke”.

Wilson told the court during the magistrate-only trial that he couldn’t remember being told about the abuse. The court heard he is potentially suffering from the early stages of Alzheimer’s disease. But in delivering his sentence Stone said Wilson was primarily motivated by a desire to protect the Catholic church and that “there is no remorse or contrition showed by the offender”.