Police have been called in to safeguard the 127-year-old sandstone building that is being eroded by people both urinating and fornicating against the walls.

The problem, which has also led to a discolouration and stench along the base of the church, was reported to police by Reverend Gordon Bradbery about six months ago.

"This has been going on for years but has become more prominent in recent times," he said.

"It's indicative of the behaviour of people in the mall, particularly those who come through inebriated.

"That sandstone is part of the original structure that was put up in 1882 so it's over 125 years old. It's just a complete lack of respect."

Wollongong Police Inspector Brian Wyver said samples taken from the building had shown a variety of human waste, including urine and semen.

"There is evidence people have also been fornicating against the church wall,'' he said.

Insp Wyver said since the church reported its concerns, regular police patrols had been conducted in the area.

"We have been issuing quite a few tickets. People should also be aware there is video surveillance in this area,'' he said.

"This isn't just an act of offensive behaviour, it's a separate crime that covers attacks on religious buildings."

Rev Bradbery said a recent escalation in the crime appeared related to an absence of public toilets in the CBD, combined with the church's location on a busy thoroughfare that linked a number of licensed premises.

"I would say probably this was because there were no public toilets around Wollongong," he said.

"There used to be some public toilets down at the Town Hall but they're now closed so there's just no facilities in Wollongong at all for people after hours."

The disturbance to church services by hooligans had also resulted in police establishing a command post outside the building on Christmas Eve.