CBS News appointed a former U.S. attorney general and a retired chief executive of the Associated Press yesterday to investigate how a botched story about President Bush's military record was researched and approved for broadcast.

Network executives picked Richard L. Thornburgh, attorney general under President George H.W. Bush - the current president's father - and Louis D. Boccardi, a former president and CEO of the worldwide news service. The inquiry is scheduled to begin this week.

Senior network officials did not comment yesterday. But in a recent interview, CBS News President Andrew Heyward said he hoped the inquiry would take "weeks, not months."

The network is reeling from a cascade of criticism in the wake of a 60 Minutes report that aired Sept. 8, which alleged that the younger Bush received preferential treatment while in the Texas Air Guard during the Vietnam era. CBS anchor Dan Rather was the on-air correspondent for the story, which relied on memos allegedly written by Bush's squadron commander. The documents were quickly attacked as forgeries. Ten days later, CBS disavowed the memos after determining that the person who provided them, retired National Guard Lt. Col. Bill Burkett, lied about how he obtained them.

"You know you're not having a great week when you discover the best news is that someone lied to you," said Bob Schieffer, CBS' chief Washington correspondent.

The network's apology, delivered Monday by Rather, and the investigation, are important steps to reassure viewers, Schieffer said. "I hope they let the chips fall where they may. Credibility is our coin of the realm."

The choice of Thornburgh, a Republican who also served as governor of Pennsylvania, could appease critics who contend that the network has a liberal bias, Schieffer said.

"CBS has two problems - the first problem is the truth," said Richard Wald, former senior vice president at ABC News. "The second problem is that of public trust and public perception."

When a producer for Dateline NBC was found to have rigged a GM truck with explosives in 1992 to illustrate a report that its design was unsafe, that network appointed an outside panel to review the incident.

"The news division didn't suffer, because they had an investigation, they found out what went wrong, and they appropriately made strong moves to fix it," Wald said.

Among the moves was the firing of NBC News President Michael Gartner.

In the CBS case, some outside critics - including the editorial page of the Hartford Courant in Connecticut, a sister paper to The Sun - have called on Rather to step down. But it is the position of the 60 Minutes producer, Mary Mapes, that looks most tenuous. Mapes, a 15-year CBS veteran based in Dallas, works for the Wednesday edition of the program, on which the Bush story aired. She recently secured photographs that broke open the story of prisoner abuse at Abu Ghraib in Iraq.

"That was one of the biggest stories that CBS News ever broke," said her former boss, Jeff Fager, now executive producer of the Sunday edition of 60 Minutes. "She's got a remarkable record of work."

Mapes, 48, also arranged for the first television interview with Essie Mae Washington-Williams, the out-of-wedlock daughter of the late South Carolina Sen. Strom Thurmond, for decades a white segregationist, and his family's black servant.

But Mapes' reliance on Burkett backfired.

Additionally, Joe Lockhart, a senior strategist for the presidential campaign of Sen. John Kerry, told reporters this week that Mapes had phoned to ask that he call Burkett. The retired Guard officer, a strong Bush critic, wanted to speak to someone senior with the Democratic campaign.

The Sun reported yesterday that Burkett had asked to be paid for his cooperation with CBS, a violation of network ethics policies. A friend said Burkett was angry that CBS did not pay him, though a network spokeswoman said Burkett was told he could not be paid.

"Something horribly wrong happened here," said Fager. "She's got some explaining to do."