WASHINGTON — CIA Director Michael Hayden has mounted a highly unusual challenge to the agency's chief watchdog, ordering an internal investigation of an inspector general who has issued a series of reports sharply critical of top CIA officials, according to government officials familiar with the matter.

The move has prompted concerns that Hayden is seeking to rein in an inspector general who has used the office to bring harsh scrutiny upon CIA figures from former Director George J. Tenet to undercover operatives running secret overseas prison sites.

The investigation is focused on the conduct of CIA Inspector General John L. Helgerson and his office, particularly whether they were fair and impartial in scrutiny of the agency's terrorist detention and interrogation programs.

Officials said the investigation also would span other subjects, and it already had expanded since its launch months ago.

U.S. intelligence officials concerned about the inquiry said it was unprecedented and could threaten the independence of the inspector general position. The investigation "could at least lead to appearances he's trying to interfere with the IG, or intimidate the IG, or get the IG to back off," one U.S. official familiar with the investigation said.

Frederick P. Hitz, who served as the CIA's inspector general from 1990 to 1998, said the move would be perceived as an effort by Hayden "to call off the dogs."

"What it would lead to is an undercutting of the inspector general's authority and his ability to investigate allegations of wrongdoing," Hitz said. "The rank and file will become aware of it, and it will undercut the inspector general's ability to get the truth from them."

Other officials described the investigation as a chance to turn the tables on an inspector general who has been accused by some of his targets of treating career officers unfairly and letting biases undermine his objectivity.

"There is across-the-board distrust with the IG function and disrespect for Helgerson, who many believe has a personal agenda on issues," said a former high-ranking CIA official who, like others interviewed, spoke on condition of anonymity because of the classified nature of the inspector general's work. Helgerson, the former official said, "always went in with a presumption of guilt."

Helgerson oversees a large staff of investigators whose activities range from detailed examinations of highly classified programs to routine audits of agency functions. He has served as inspector general at the CIA since 2002.

Hayden, an Air Force general who became CIA director last year, has not been involved in any publicly known clashes with Helgerson. But Hayden has been a staunch defender of the Bush administration's counterterrorism programs and has lamented publicly what he describes as a tendency by outside observers and critics to second-guess the activities of the nation's intelligence agencies.

In response to questions about the unusual arrangement, CIA spokesman George Little said Hayden "firmly believes that the work of the Office of Inspector General is critical to the entire agency, and, since taking the helm at CIA, he has accepted the vast majority of its findings."

The CIA's review is being led by Robert Deitz, an attorney with long-standing ties to Hayden who was brought in to serve as a senior counselor to the director. Deitz, who served as general counsel at the National Security Agency when Hayden was director there in the 1990s, has assembled a small team of investigators.

The inquiry has been driven in large part by senior operations officers complaining to Hayden that they were unfairly criticized by Helgerson in classified reviews of the CIA's secret prisons programs.

Among the issues being explored are whether agency officers were given adequate opportunity to defend their actions and whether the inspector general's conclusions accurately represented their roles.

The CIA created a network of secret overseas prisons shortly after the terrorist attacks of Sept. 11, 2001. The agency has faced severe international criticism for employing harsh interrogation tactics as well as a program known as "extraordinary rendition," in which prisoners have been transferred to countries known to use torture.

The focus on the prison program represents an expansion of an investigation that officials said began several months ago into the relationship between Helgerson's office and that of the CIA general counsel.

One former high-ranking CIA official said Helgerson did not shy away from taking positions in heated internal policy debates.

Helgerson has become an unusually high-profile occupant of the position largely because his tenure has coincided with a series of historic intelligence blunders.

An examination of failures leading up to the Sept. 11 attacks was sharply critical of Tenet and other senior CIA officials, saying they "did not discharge their duties in a satisfactory manner" and calling for the creation of special in-house panels to determine whether they should be reprimanded.

The conclusions were denounced by many of the targets of that investigation, including Tenet, who issued a statement saying, "The IG is flat wrong."

Because of its role, the inspector general's office is viewed with distrust by other parts of the agency, particularly case officers who operate overseas and "feel they're being investigated by people who don't fully understand their business," one former CIA official said.

The relationship between the CIA director and the inspector general is complicated. The law creating the watchdog position specifies the IG "shall report directly to and be under the general supervision of the director." The law also makes clear the CIA director can ignore recommendations from an IG and even prohibit investigations.

But Hitz, the former CIA inspector general, and others said the position traditionally had operated with a great deal of autonomy, and there were other mechanisms for holding an inspector general accountable. In particular, a 1992 executive order established what is known as the President's Council on Integrity and Efficiency and gave it authority to evaluate the work of inspector generals in agencies across the government.

"I don't think it's appropriate for the IG to be in an off-line way investigated by his superior," Hitz said. "If the director has a problem with the way the IG is performing his job, he can go to the Congress, to the president's intelligence oversight board or he can go to the president himself."