BUFFALO, N.Y. -- The Roman Catholic Diocese of Buffalo, New York, is firing back at a former assistant-turned-whistleblower who says Bishop Richard Malone should resign over his response to reports of clergy sexual misconduct.

In a statement just before midnight Tuesday, the diocese called statements made by Siobhan O'Connor during an earlier news conference "embarrassingly contradictory." It attached emails from O'Connor praising Malone.

O'Connor, who worked closely with Malone as his executive assistant for three years, secretly copied and leaked confidential files she says show Malone allowed an accused priest to remain on the job and excluded dozens of others from a list of problematic priests released publicly this year. The hundreds of pages she uncovered included personnel files and memos. Last week, she spoke with the FBI.

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"The reality of what I saw really left me with no other option," O'Connor told "60 Minutes." "Because at the end of my life, I'm not going to answer to Bishop Malone. I'm going to answer to God."

At first, she took pictures with her phone. Then she used the copy machine at the bishop's offices.

Malone has said he made mistakes with cases involving adult victims but never knowingly left a priest accused of child abuse in ministry.

O'Connor on Wednesday called the bishop's response to her comments a "needless deflection" from the issues.

The Roman Catholic Church is facing its biggest crisis in the United States since the Boston sex abuse scandal 16 years ago. Thirteen states are now investigating whether abuse was concealed by church leaders, including bishops who head each diocese.