WASHINGTON, May 19 - Robert C. Pozen, the business executive who developed the theory behind President Bush's plan to trim Social Security benefits in the future, urged the president on Thursday to drop his insistence on using part of workers' taxes to pay for individual investment accounts.
This was one of two blows during the day to Mr. Bush's policies on Social Security and retirement saving. In the House, Representative Bill Thomas, chairman of the Ways and Means Committee, disregarded the methods favored by the president to encourage workers to save for retirement - mostly tax incentives for the affluent - and offered completely different proposals of his own.
The president's Social Security and retirement measures have faced trouble in Congress all year, and the developments on Thursday raised further doubt about their prospects.
On the question of Mr. Pozen's new position, Trent Duffy, a White House spokesman, said, "The president is committed to a voluntary personal account as part of a comprehensive Social Security modernization plan."
On Mr. Thomas's stance on retirement saving, Mr. Duffy said Mr. Bush "understands and welcomes the chairman's ideas."
Mr. Pozen, a member of Mr. Bush's advisory commission on Social Security in 2001, said at a forum at the Treasury Department that the president's approach to investment accounts would destroy the chances for a Social Security bill in Congress and would make it more difficult to resolve the long-term financial problems facing the system.