Most of the complaints were filed by current and former employees of his own office, the newspaper reported.

Written complaints and supporting documents from at least 16 people allege Cobb suppressed investigations of wrongdoing within NASA and abused and penalised his own investigators when they persisted in raising concerns, the newspaper reported.

The complaints were being reviewed by the FBI-led Integrity Committee of the President's Council on Integrity and Efficiency, the article said.

In documents obtained by The Washington Post and in interviews, current and former NASA employees said Cobb's actions had contributed to a lack of attention to safety problems at the space agency, the newspaper said.

In an interview with the Post, Dennis Coldren, retired manager of NASA space station and space shuttle audits, was one of several associates to describe Cobb as a "bully."

Coldren also alleged that, just weeks before the February 2003 Columbia space shuttle disaster, Cobb quashed efforts to inquire into cancelled funding to upgrade deteriorating gantries, launch pads and other shuttle infrastructure.

The shuttle disintegrated upon re-entry, killing all seven astronauts aboard, and the shuttle fleet was grounded, except for one flight to the International Space Station last summer.

The petitioners said Cobb had disregarded the inspector general's mandate to root out "waste, fraud and abuse" and caused dozens of longtime NASA employees to leave the IG's 200-person office, the newspaper reported.

Cobb, appointed by President George W Bush in 2002, would not discuss his case in a telephone interview, the paper said. But he was quoted as saying that he would co-operate fully with the investigation.

Cobb, who worked as an ethics lawyer in the office of the White House General Counsel under Bush, sent an e-mail to his staff on Tuesday urging them to "co-operate fully" with investigators, the newspaper said.   

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