Alex Wong / Getty Images, file

Director of the Missile Defense Agency Army Lt. Gen. Patrick O'Reilly testifies during a hearing before the U.S. Senate Armed Services Committee on September 24, 2009. He is described as a bullying manager in a report dated May 2, 2012.

WASHINGTON - The U.S. Missile Defense Agency's chief routinely bullied his senior staff, chilling discussion of thorny issues in the multibillion-dollar program he runs, the Defense Department's inspector general said in a report made public on Tuesday.

Army Lieutenant General Patrick O'Reilly, who has headed the Pentagon arm since November 2008, demeaned and belittled subordinates, making them reluctant "to speak up and raise issues during meetings with him," said the 19-page report dated May 2.

The agency is developing, testing and fielding a layered shield against ballistic missiles that could be fired by countries like Iran and North Korea.

It manages research, development, testing, purchases and stitching together complex systems on land, at sea and sensors in space.

Russia tests missile designed to counter US defense shield

The $10 billion-a-year effort has a long record of flight-test failures and successes as well as the biggest research budget of any Pentagon program. Some critics have derided it as a boondoggle for contractors including Lockheed Martin Corp, Boeing Co, Raytheon Co and Northrop Grumman Corp.

The inspector general interviewed O'Reilly and 33 other witnesses with knowledge of the matters at issue for a preliminary report. Another four were added at O'Reilly's request, but they were not in a position to comment on certain events at issue, the report said.

Several witnesses testified that fear of O'Reilly's reactions "impeded the flow of information," the investigation found. It was first reported by The Cable, a Web-based newsletter of Foreign Policy magazine.

'US Navy lit up the sky': Interceptor for Europe anti-missile shield tested off Hawaii

A spokeswoman for the inspector general, Bridget Serchak, said such reports typically were made public only after receipt of at least three requests for them under the Freedom of Information Act.

'Dirt beneath his feet'
The report said five witnesses told inspectors that O'Reilly's leadership, described by the investigators as marked by yelling and screaming, was either the main factor or a contributing factor in their decision to leave the agency.

"We received consistent testimony that as a result of his management style, even senior officials stopped communicating" with O'Reilly, the report said.

Leon Panetta seeks another $70 million for Israel's 'Iron Dome' rocket shield

The inspector general recommended the secretary of the army consider "appropriate corrective action" with regard to O'Reilly. Army representatives did not return phones calls seeking comment.

The Cable quoted some descriptions of O'Reilly's leadership style highlighted in the report, including:

• The worst manager I've worked for in 26 years of public service
• As a leader, as a director, whatever, he's the worst
• In terms of leadership, bottom
• Absolutely last, out of all the generals I've served under
• Without a doubt ... the worst leader I've worked for, the worst
• He has probably been 100 degrees out from everything I've learned about leadership
• How not to act
• What doesn't kill you makes you stronger
• Not the command climate I would have set

One witness described his personality as "Dr. Jekyll and Mr. Hyde," The Cable said.

"LTG O'Reilly would 'berate you, make you feel like you're the dirt beneath his feet,' then pay a compliment to rebuild the employee and later repeat that cycle," the report said.

Highly intelligent
O'Reilly, in a response summarized in the final report, questioned the accuracy of witness testimony and denied engaging in many of the alleged brow-beating practices.

He stated that he had initiated weekly meetings with top aides to make sure that effective lines of communication stayed open. Richard Lehner, a spokesman for the Missile Defense Agency, had no comment on the report.

A majority of the witnesses testified that O'Reilly was highly intelligent, "even brilliant," and possessed a high degree of expertise in managing purchases, the report said.

Reuters contributed to this report.

More content from msnbc.com and NBC News:

• Kids cross border alone, fleeing drugs and games
• Fire evacuation sparks panicked pet exodus
• Inmate serving life sentence won't be charged in killing of another prisoner
• Independence Day irony: PTSD has many vets dreading, avoiding fireworks
• Could you pass the US citizenship test?
• T-shirt fundraiser for wildfire relief takes off
• Video: Casino seeks machine gun range
• The doctor will see you now, for $5

Follow US News on msnbc.com on Twitter and Facebook