Celebrant who allegedly performed an illegal marriage charged.

A 35-year-old man, believed to be a Muslim religious leader, was arrested outside Parramatta Police Station on Monday afternoon.

He was charged with solemnisation of a marriage by an unauthorised person, and released on bail to appear in Parramatta Local Court in April.

"I'm delighted charges have been laid," Mr O'Farrell told reporters.

"This charging of this person sends a strong message, whether to religious celebrants or civil celebrants."

Police revealed last week that a 26-year-old man met a 12-year-old girl in the Hunter region in 2013 and allegedly became involved in an ongoing sexual relationship with her.

Police say the man and child, who is now 13, took part in the Islamic ceremony in NSW earlier this year.

The girl and the man allegedly moved to a house in Sydney's southwest after the ceremony was conducted.

He was charged with 25 counts of sexual intercourse with a child between 10 and 14 years of age and is expected to make an application for bail on Wednesday.

Investigations by the State Crime Command's Child Abuse Squad are continuing and police are not ruling out further arrests.