A drunk Catholic priest caught in a car with two prostitutes and his pants around his ankles was a regular customer of the women, the child abuse royal commission heard.

"He was pissed to the eyeballs with his strides around his ankles," former Victorian policeman Denis Ryan recalled.

Mr Ryan and two other officers had pulled over a car that kept bumping into the gutter in St Kilda in early 1956.

The driver was a well-known prostitute named Hazel, Mr Ryan told the commission.

"There was another prostitute and laying across, with his head on the driver and his feet on the other prostitute, was a man with his pants down around his ankles, his genitals showing," Mr Ryan said.

"He was wearing a Catholic priest's collar and on the floor was an empty sherry bottle. Hazel again said to us: 'He allows us to drive the car. He's a regular customer of ours.'"

Once back at the station, Mr Ryan found out the man was Apollo Bay priest Fr John Day. Mr Ryan said the drunk priest had to be carried and dragged into the sergeant's office and was later picked up by two priests.

"The priest was completely inebriated to the extent that he had to be half-dragged out there," Mr Ryan said.

Mr Ryan later asked the sergeant why Day was not charged.

"(He) explained that the Catholics looked after the Catholics and the Masons looked after the Masons, and short of murder you just didn't charge a priest," Mr Ryan said on Tuesday.

As fate would have it, Mr Ryan ran into the drunk priest again, when stationed in Mildura in 1962.

He recognised Day but the priest claimed the drunk was not him - it was another priest in Apollo Bay of the same name.

"I said 'no you're a liar, it was you'," Mr Ryan said.

"He told me to get out of the presbytery."

Mr Ryan's attempts to investigate child sex abuse claims against Day in Mildura in 1971 and 1972 were stymied by both the church and other police officers, the inquiry heard.

Fifteen people have made child sex abuse claims against Day to the Diocese of Ballarat, covering 1954 to 1973.

All the claims were made after Day's death in 1978.