DETROIT (AP) — Time and time again, General Motors Corp.'s board of directors reaffirmed its support for chairman and chief executive officer Rick Wagoner, even as the company piled up billions of dollars in losses and begged for government loans to stay alive.

But Wagoner is now a high-profile casualty of government intervention, forced out as part of the Obama administration's sweeping last-ditch effort to save the century-old auto giant.

Wagoner, 56, who spent 32 years with GM working all over the world, stepped down effective immediately, the company said in a statement early on Monday. He was replaced as CEO by Fritz Henderson, the company's vice-chairman and chief operating officer.

GM board member Kent Kresa, a former chairman and CEO of Northrop Grumman Corp., was named interim chairman and said new directors will make up the majority of GM's board when a new slate is nominated for election at the company's annual meeting in August.

"The board has recognised for some time that the company's restructuring will likely cause a significant change in the stockholders of the company and create the need for new directors with additional skills and experience," Kresa said in a written statement.

GM shares tumbled 92 cents, or 25.4 percent, to $2.70 on Monday. That is down 89 percent from their 52-week high of $24.24 on April 30, 2008.

The management shake-up, according to several industry analysts, shows that the administration is serious about forcing GM to change more quickly and dramatically than it did during Wagoner's nearly nine-year tenure as CEO.

Jeremy Anwyl, chief executive of the automotive website Edmunds.com, called the move "political theatre" to appease an increasingly bailout-weary public.

"American taxpayers are not happy," Anwyl said. "But this way you're able to point to Rick and say he's gone, and that creates an environment where the loans become politically palatable."

By all accounts, Wagoner made progress in fixing GM. While CEO, he cut its US work force from 177,000 to roughly 92,000 today.

Wagoner also closed factories; shed the unprofitable Oldsmobile brand; globalised GM's engineering, manufacturing and design to save billions; and led a resurgence in quality and performance of its long-neglected cars. In 2007, the company reached a landmark agreement with the United Auto Workers that shifted massive retiree health care costs to a union-run trust and ushered in a $14-per-hour wage for new hires, about half that of a current labourer.

But critics, including many members of Congress, say Wagoner moved too slowly, failing to cut enough of the company's huge health care and pension costs, and relying too long on high-profit pickup trucks and SUVs as gas prices rose and the market shifted toward smaller vehicles.