The country's first commission of inquiry into child sexual abuse within the Catholic Diocese of Maitland-Newcastle has started in Newcastle this morning.

In her opening address to the Newcastle Supreme Court, Commissioner Margaret Cunneen SC said the Hunter region had been deeply effected by matters of child sexual abuse within the church.

“It has rightly been said that child sexual abuse is no longer a crime in which the conspiracy of silence ­continues to the grave,” Ms Cunneen said. “Children are inherently vulner­able and innocent. The sexual abuse of children is abhorrent.

"It exploits their vulnerability, irreparably ­damages their innocence and casts a shadow over their whole lives."

Detective Chief Inspector Peter Fox, whose investigations brought about the inquiry, will give evidence this morning.

Counsel assisting Julia Lonergan SC said Mr Fox was ordered to cease investigating allegations of abuse by paedophile priests Denis McAlinden and Jim Fletcher in 2010.

Ms Lonergan said Mr Fox was so concerned by the direction of investigations he participated in an interview with the ABC's Lateline in 2012.

His allegations that the Catholic Church had 'covered up' child sexual abuse contributed to the establishment of the inquiry.