One of the highest ranking members of the Catholic church in Australia, bishop of Broome Chris Saunders, has voluntarily stood aside from his position amid serious allegations.

On Wednesday the Perth archbishop, Timothy Costelloe, said Saunders had “voluntarily stood aside” from his position after the Vatican announced an internal investigation into the diocese.

It comes as Seven News reported on Wednesday that Western Australia police had been investigating claims of sexual misconduct made against the bishop since October 2018. The Guardian has confirmed there is an ongoing investigation into a complaint of an historical sexual assault, however no charges have been laid.

In a report aired on Seven on Wednesday night, Saunders vehemently denied the claims. He said: “That’s extraordinary. Without any doubt whatsoever, without any reservation, that has never happened and it never would happen.”

In a statement, Costelloe said Saunders had “voluntarily stood aside” after Rome appointed an “apostolic visitator” to review the running of the Broome diocese.

Costelloe said the Vatican had made the decision “conscious of the particular situation in the diocese of Broome and concerned for the pastoral care of the clergy, religious and laity of the diocese”.

“Bishop Christopher Saunders, in order to allow the apostolic visitator the freedom to carry out his duties, has voluntarily stood aside from the ordinary administration of the diocese for the duration of the visitation,” Costelloe said in a statement.

An apostolic visitator is a church-appointed officer instructed to conduct what one Catholic official described as an internal “health check” of the diocese.

In a statement WA police said it would investigate “any allegations of criminal sexual misconduct”.

“WA police force will not comment on allegations made against specific individuals,” a spokeswoman said.

Saunders first joined the Broome parish of the Catholic church in 1975 and was appointed bishop in 1995.