A panel of prominent lay Catholics has accused the nation's Roman Catholic bishops of backsliding on their promises and seeking to return to "business as usual" since media attention to the clergy sex abuse scandal began to fade this year.

In a heated exchange of letters made public yesterday, some bishops in turn accused the 13-member National Review Board of using offensive language and assuming "the worst motives on the part of the bishops."

The letters reveal that the relationship between the bishops and their handpicked advisory board has become severely strained for the second time in a year. Last June, the board's original chairman, former Oklahoma governor Frank R. Keating (R), resigned after comparing some bishops to the mafia in their devotion to secrecy.

Keating was replaced by Anne M. Burke, a justice of the Illinois Appellate Court. Under her direction, the board oversaw sexual abuse "audits" of all U.S. dioceses last year. On Feb. 27, it released a pair of landmark studies that found that 4,392 U.S. priests had been accused of child molestation since 1950 and placed much of the blame on bishops and seminaries.

The heated correspondence, posted by the weekly National Catholic Reporter on its Web site yesterday, began a few weeks later. In a March 29 letter to Bishop Wilton D. Gregory, president of the U.S. Conference of Catholic Bishops, Burke complained that the board had not been told until after its Feb. 27 news conference that key bishops were determined to prevent or postpone until November a second round of audits, which are designed to check their compliance with the church's child protection policies.

Burke said the board felt "manipulated" for public relations purposes. "We are very disheartened by this apparent decision to go back to 'business as usual,' " she wrote. "A decision to backslide on the Charter and Norms -- and it is hard to see the decision to delay matters until November as anything else -- will delay the necessary healing and reopen the wounds of deception, manipulation and control -- all the false ideals that produced this scandal."

Gregory forwarded Burke's letter to all the bishops, some of whom responded with pique. "Your language is designed to offend and contains implicit threats that are, to put it mildly, inappropriate for anyone of your professional stature," wrote Denver's Archbishop Charles J. Chaput and Auxiliary Bishop Jose H. Gomez.

A spokesman for the bishops' conference, Monsignor Francis Maniscalco, said yesterday that the bishops may address the conflict at their semiannual meeting in June, when they will take up the question of a new round of audits. "Both the board members and the bishops have said strong things over the past year, because a lot is at stake," Maniscalco said. "But I think everybody in this matter is committed to the church successfully resolving this situation."

Washington lawyer and board member Robert S. Bennett said in a telephone interview that relations with the bishops are not "poisoned." But, he said, "we're all concerned that rather than building on what we've done, there are some bishops who want to retrench."