WASHINGTON – Beleaguered U.S. Homeland Security Secretary Michael Chertoff testified yesterday that he did not take charge of his department’s faltering response to Hurricane Katrina because his personal experience during the September 11 terrorist attacks had convinced him that micromanaging by senior officials could make matters worse.

But members of the Senate Homeland Security and Government Affairs Committee, which has spent months probing the disaster, sharply criticized Mr. Chertoff for being so out of touch with the unfolding disaster that he went to bed unaware that the New Orleans levees had collapsed hours before, killing and injuring hundreds of people and leaving much of the city under water.

Committee chairwoman Susan Collins, a Republican of Maine, said it was disheartening that Mr. Chertoff was “consistently behind the curve.” Katrina made landfall on Monday, August 29, and a storm surge smashed the New Orleans levees later that day. Mr. Chertoff said he went to sleep Monday night not knowing his department had been informed of the levees’ collapse.

Mr. Chertoff, who testified for almost three hours before the Senate committee, acknowledged that his department had received e-mails describing the unfolding catastrophe, but he said his staff decided to withhold information from him until it had been verified by what he called “ground truth” – again because of his experience during September 11, when top officials were bombarded with imprecise data and unchecked rumors. He said he has since taken steps to make sure that would not happen in future.

In the months after Katrina, criticism of the botched federal response focused primarily on the Federal Emergency Management Agency and its director, Michael Brown, who resigned under fire. But FEMA is part of the Homeland Security Department, and as investigators have dug deeper, the spotlight has shifted to Mr. Chertoff because of his failure to step in despite clear signs that the response was going awry.

Although Mr. Chertoff was hailed as a brilliant choice when President Bush chose him to head up the department more than a year ago and was confirmed unanimously by the Senate, the criticism of his conduct during Katrina has become so pointed that a House special investigating committee titled its 600-page report “A Failure of Initiative.” It chided Mr. Chertoff for being too passive. The report was released yesterday, although many of its findings had been reported earlier.

In its opening pages, the House report noted a succession of steps Mr. Chertoff “should have” taken, both before Katrina hit the Gulf Coast and after the government began to stumble. Most if not all the steps, the report noted, were part of the elaborate procedures that had been developed for responding to disasters.

The House report was especially devastating for Mr. Chertoff and the Bush administration because it was written largely by Republicans – Democrats boycotted most of the committee’s sessions – and because it painted the government’s failures with a broad brush. “Secretary Chertoff failed to take the reins from (Mr. Brown) quickly enough,” said committee chairman Rep. Tom Davis, a Republican of Virginia, adding, “The White House failed to act on the massive amounts of information at its disposal.”

On the Senate side, Ms. Collins particularly criticized Mr. Chertoff for waiting until after the disaster had struck to designate a point person to manage the federal response, as called for in the government’s advance plan. “That’s like having the generals show up after the battle had already begun,” she said.

Mr. Chertoff said he had thought FEMA knew more about dealing with hurricanes than anyone else in government.

Questioned on his failure to work closely with FEMA, Mr. Chertoff said he knew his relationship with Mr. Brown was strained, but said it never occurred to him that Brown deliberately would ignore the secretary and established procedures for coordinating the response.

Mr. Brown testified last week that he felt it would “waste my time” to consult with Mr. Chertoff.

In explaining his failure to be proactive, the secretary recalled that he had been serving as assistant attorney general for the criminal division of the Justice Department when terrorists struck the Pentagon and the World Trade Center. “I was on duty on 9/11,” he said.

After the attacks, he said, high-level bureaucratic infighting hampered efforts to deal with the attacks and pursue the perpetrators.

He said he was trying to avoid that mistake with Katrina. “I didn’t want to get in their hair,” he said of FEMA and other operations managers.