The white House and Congress must share some blame for the crash of the Columbia space shuttle that killed seven astronauts, the chairman of the Columbia Accident Investigation Board said on Thursday.

　　Retired navy Admiral Harold W. Gehman Junior told the House Science Committee that following past tragedies, NASA has made management changes, but that the space agency responds to budgetary and other pressures by reverting to practices that are less safe.

　　"After a tragedy, they take a whole lot of management actions," Gehman said. "But over the years forces begin to act on them. Some are budget pressures from both ends of Pennsylvania Avenue" - a reference to Congress and the White House.

　　He said the space shuttle management gets squeezed by budget pressures and schedules and takes money away from some measures that assure safety.

　　"We find this to be unhealthy," Gehman said.

　　Gehman and three members of the Columbia Accident Investigation Board fielded questions from the committee. They told lawmakers that the National Aeronautics and Space Administration must change its culture if the shuttle is to fly safely again. They also said the nation needs to establish a vision of specific goals for the human spaceflight program.

　　In response to questions, Gehman said that the board found that NASA's budget, which is controlled by the White House and by Congress, played a role in the February 1 accident.

　　"A constricted and squeezed budget was a contributing factor" in the accident, Gehman said.

　　In response, the committee chairman, Representative Sherwood Boehlert said, "We share some of the responsibility, but changes are needed" in NASA.

　　Boehlert said it was NASA management that made decisions to shift money around in the agency and to build an internal system that put less emphasis on safety.

　　He said even if NASA "got a blank check," some of the agency's decisions that contributed to the Columbia accident would not have been affected.

　　Just as he did during testimony before a Senate committee on Wednesday, Gehman said the board believes there should be a personal accounting for the managers who had a role in the Columbia accident.

　　Nasa administrator Sean O'Keefe said he did not believe the people were guilty of anything but bad judgment and that "there is no principle of accountability that says there has to be a public execution."