U.S. Catholic bishops are planning to appoint a nun to their lay review board on sexual abuse, a step that could undermine the watchdog panel's independence, several of its members charged this week.

The board of 12 prominent Roman Catholic laypeople, appointed by the bishops two years ago, has had several public confrontations with the church hierarchy. Its first chairman, former Oklahoma governor Frank Keating (R), resigned in June 2003 after comparing a few bishops to "La Cosa Nostra" in their devotion to secrecy. The board also issued a stinging report in February that blamed bishops for decades of tolerating and hiding sexual abuse of minors by priests.

"Given the experience we've had in two-plus years now, we know this is very difficult work and requires at times taking a very tough stance," said board member Jane Chiles, a former lobbyist for Catholic causes in Kentucky. "It's difficult enough for a layperson to do that. I can't imagine a nun doing it."

A spokesman for the U.S. Conference of Catholic Bishops, Monsignor Francis Maniscalco, declined to confirm or deny that the bishops intend to appoint a nun to the high-profile board. "It's a confidential process," he said.

Several board members said the bishops' administrative committee deviated from the expected appointment process last week by choosing Sister Carol Keehan, former president of Providence Hospital in Washington, to fill one of at least four openings on the all-volunteer board. They said Keehan was not among nine nominees submitted jointly by the review board and the bishops' Ad Hoc Committee on Sexual Abuse.

Keehan, who moved to Pensacola, Fla., this year to become chairman of a group of Catholic hospitals, said yesterday that she had not realized she was under consideration. "I have not been offered a position, and I'm not sure whether I would accept," she said. "I'd have to sort out whether it would be divisive or positive . . . because it's very important to me that the review board be successful."

Washington lawyer and board member Robert S. Bennett stressed that the board is not objecting to Keehan personally. "I know Sister Carol. She is a gifted, rare human being . . . and will not be a rubber stamp for anybody," he said.

Although the church considers nuns to be laity, Bennett and others said the appointment could set a precedent for naming more nuns and priests to the board. "It would begin to breach a wall that has served us well," said board member William R. Burleigh, chairman of the E.W. Scripps newspaper company.

Anne M. Burke, an Illinois judge and the board's outgoing chairman, first disclosed the appointment in a Sept. 20 speech at Loyola University Chicago in which she described the plan as evidence of "mischievers at work" in the bishops conference, according to the Chicago Tribune.