SEATTLE — Washington Mutual Corp., hard-hit by the mortgage and credit crises, said Monday it will replace Chief Executive Kerry Killinger as chairman of the board and take other steps to improve corporate governance.

Killinger, 58, will remain on the board where he has served as chairman of the country's largest savings and loan since 1991. He will also hold his post as chief executive, even as the list of CEOs shown the door at the country's top banks continues to grow.

Wachovia Corp. said Monday it had asked CEO Ken Thompson to step down, joining Merrill Lynch & Co.'s Stanley O'Neal and Citigroup Inc.'s Charles Prince among the ousted.

At WaMu's April shareholders meeting, a nonbinding resolution urging the installation a non-employee as board chairman passed with 51.5 percent of the votes.

WaMu said Stephen E. Frank, the lead director on its board, will become chairman starting July 1. Frank, 66, retired in 2002 as CEO of Southern California Edison, the largest subsidiary of the Edison International power company.

In addition to splitting the job of chairman and CEO, WaMu said its board made has made it harder for directors in uncontested elections to hold their seats if they don't get a majority of the votes.

The board also shuffled the leadership for committees that some shareholders blamed for heavily exposing the thrift to the subprime mortgage crisis, despite signs that the housing market was teetering on collapse.