Garry Prokopishin, a former foster parent, faces several sex-related charges. (CBC)

Police in Calgary have laid more criminal charges against a former foster parent who is accused of paying teenage boys in his care for sex.

Garry Prokopishin, 51, was arrested and charged Tuesday with obtaining or attempting to obtain sex from a person under 18 and with inciting sexual contact with a youth by a person in authority, police said.

The incidents are believed to have happened between December 2004 and June 2008. The alleged victim was in his mid-teens, police said.

In February, the same charges were laid against Prokopishin in connection with three other alleged victims. Those incidents are said to have occurred between January 2006 and April 2008.

Fifty-five foster children, all boys between the ages of 14 and 17, have lived under Prokopishin and his wife's care in the past 20 years, police said.

The investigation is continuing and interviews are being conducted across Canada, officials said.

Prokopishin's foster home was suspended in June 2009 when the investigation was launched. There are no children in the home now.

The Alberta Foster Parent Association named Prokopishin one of the foster parents of the year for 2006.

Prokopishin served as a director of the Calgary and District Foster Parent Association.