The Movement to Restore Trust, an independent Catholic organization, has called on Buffalo Bishop Richard Malone to resign.
It comes following increasing calls for Bishop Malone to step down after another whistleblower came forward Wednesday.
The group says it was a very difficult decision that was arrived following "lengthy prayer, reflection and discussion."
In a statement, the group said while it has made progress toward restoring trust in the diocese by working with Bishop Malone, recent events have led them to realize further progress is not possible.
It says the Vatican should appoint a temporary diocesan administrator with no ties to the diocese, while it considers the appointment of a permanent bishop.
The group says it will be contacting Cardinal Timothy Dolan, the archbishop of New York, and other members of the Catholic Church across the state.
It is also formally pulling out of commitments with the diocese until Bishop Malone resigns.
Calls for Bishop Malone to resign have been made for more than a year. Whistleblower Siobhan O'Connor and others at a peaceful protest Thursday were pleased with MRT joining their side.
"We didn't know what to expect from them and we are thrilled they finally realized there's no going back with regards to Bishop Malone," said O'Connor.
Bishop Malone reiterated on Wednesday he will not resign and says he feels he has the support of a majority of the Catholic faithful.
If Bishop Malone does not step down, John Hurley, president of Canisius College and a leader in MRT, says the only way he can be removed is if the pope calls for his removal.
The Catholic Diocese of Buffalo did not immediately return a request for comment, saying the bishop's schedule was too busy Thursday to comment.
Spectrum News did, however, learn the listening session at Niagara University on Wednesday is officially canceled.