The Justice Department and FBI delayed notifying prosecutors in scores of death-row convictions that their cases might have relied on flawed FBI forensic work, the department’s Office of Inspector General reported Wednesday.

In a scathing report that shed new light on one of the FBI lab’s worst modern scandals, the inspector general said the Justice Department didn’t properly review all of the cases by FBI examiner s whose work was known to be flawed.

The report said the FBI took more than five years to identify more than 60 death-row defendants whose cases had been handled by 13 lab examiners whose work had been criticized in a 1997 inspector-general investigation.

As a result, state authorities could not consider whether to stay sentences, and three men were put to death. One of those defendants, who was executed in Texas in 1997, would not have been eligible for the death penalty without the FBI’s flawed work, the report said.

“Failures of this nature undermine the integrity of the United States’ system of justice and the public’s confidence in our system,” the 146-page report stated. The failure to admit errors at the time “also injured the reputation of the FBI and the Department.”

The report was requested by Rep. Frank R. Wolf (R-Va.) after The Washington Post reported in 2012 that Justice officials knew for years that flawed evidence and testimony might have led to the convictions of innocent people. The Post focused on the Texas case and three men in Washington, D.C., who were represented by the Public Defender Service and have been exonerated.

Problems at the FBI lab first surfaced in the early 1990s, when scientist-turned-whistleblower Fred Whitehurst reported that sloppy work by examiners was producing unreliable forensic testimony. Justice officials launched a task force that was active from 1996 to 2004 to ensure that potentially exculpatory evidence involving criticized agents was turned over to defendants.

But The Post found that such notification rarely happened and that not all flawed cases were properly reviewed.

Justice Department officials, responding to Wednesday’s report, said that they had been diligent in trying to protect defendants’ rights in undertaking a review of unprecedented size and complexity.

However, “with the benefit of hindsight, the Department agrees that certain aspects of the Task Force review could have been more efficient or effective,” Brette L. Steele, senior adviser on forensic science, wrote in a department memo included in the report.

As of October, the 26 surviving death-row inmates whose cases were included in the review had all been notified that their convictions had been re-examined, Steele said. The inspector general had recommended the notifications and retesting of evidence in 24 death-row cases in which the defendant was deceased.

The inspector general’s office said the department should notify all 2,900 defendants whose cases were reviewed by the task force, starting with 402 defendants whose cases were so problematic that the task force obtained a fresh scientific review. Their names were made public Wednesday for the first time.

The report said that even more defendants’ cases should have been reviewed but were omitted for inappropriate reasons, and the scope of errors never would be known. For many defendants, it said, “delays were very prejudicial and, for some, they caused irreversible harm.”

The report also stated that the FBI agent responsible for the greatest number of problem cases, hair examiner Michael P. Malone, was transferred to field work until he retired in 1999. He then became a contractor to the agency from 2002 until last month, conducting security investigations, the report said.

“We believe that Malone’s employment as an FBI contractor was a consequence of the failure of the FBI and the Department to discipline Malone for the misconduct we identified in our 1997 Report,” Wednesday’s review said.

In an interview, Whitehurst said it’s “preposterous” that two decades after he reported the forensic problems, the FBI is still allowed to re-examine its own mistakes. “When we divert our attention, we’ll be back where we were before,” he said.

Sen. Chuck Grassley (R-Iowa), ranking Republican on the Senate Judiciary Committee, called Wednesday’s findings “shocking” and criticized the FBI for “foot-dragging and resistance to accountability.”

“The initial shoddy lab work was compounded by the Justice Department’s unconscionable failures to fix the problems it caused in hundreds of cases,” Grassley said. “The FBI and the Justice Department will have a lot of work to do to restore the public’s confidence in their integrity following these revelations.”

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