Pastors of the United Methodist Church rarely find themselves amid financial controversy, let alone one causing alarm in both the White House and the boardrooms of corporate America. Yet the 25,000 US churchmen are an unlikely example of an issue that is fast becoming the toughest challenge facing private pensions for a generation.

Church leaders bucked the trend this year by deciding to do what few other large employers have dared: they launched a retirement plan promising to provide guaranteed pensions to its members.