SYDNEY, Australia: Australian police detained and charged on Monday a well-known cult leader known as "Little Pebble" for allegedly grooming a child while in jail.

William Costellia Kamm, 73, and his partner Sandra Costellia, 58, were arrested after a six-month investigation, and were refused bail to appear in court on Tuesday.

Costellia Kamm founded the "Order of Saint Charbel" in the rural town of Nowra in the 1980s and preached a doomsday Christian message.

He previously spent nine years in jail for having sex with two teenage girls before being paroled in November 2014.

Police said a 19-year-old woman alleged the couple groomed her from age 6.

The girl "was advised by the religious leader and his partner that she had been selected to procreate with that religious leader to build a new sect," said Jayne Doherty, commander of the New South Wales Police sex crimes squad.

"The male accused was an inmate at a correctional center and utilized various methods, such as phone calls and letters, and used the female ... co-accused in that matter to groom that child, and gave her gifts and certain directions in relation to that grooming," she added.

Doherty called the allegations "horrendous," particularly because they had occurred during the girl's formative years.

Costellia Kamm faced several charges related to the alleged grooming, as well as a charge for failing to comply with a supervision order.

His partner was charged with two counts related to grooming a child.

The couple was being held at a police station in the eastern city of Sydney.