WASHINGTON — The former F.B.I. director James B. Comey was “insubordinate” in his handling of the investigation of Hillary Clinton during the 2016 presidential election, a critical Justice Department report has concluded, according to officials and others who saw or were briefed on it.
But the report, by the department’s inspector general, Michael E. Horowitz, does not challenge the decision not to prosecute Mrs. Clinton. Nor does it conclude that political bias at the F.B.I. influenced that decision, the officials said.
“We found no evidence that the conclusions by department prosecutors were affected by bias or other improper considerations,” the report said, according to one official who read the sentence to The New York Times. “Rather, we concluded that they were based on the prosecutor’s assessment of facts, the law, and past department practice.”
The report has been highly anticipated in Washington, not least by President Trump, who has argued that a secret coterie of F.B.I. agents rigged the investigation to help Mrs. Clinton win the presidency. The findings, as described by officials who spoke on condition of anonymity before the report’s release Thursday afternoon, cite no evidence to support that theory.
Nevertheless, the report paints an unflattering picture of one of the most tumultuous periods in the 110-year history of the F.B.I., when agents investigated Mrs. Clinton’s use of a private email server to store classified information and the Trump campaign’s connections to Russia.
The report criticizes the conduct of F.B.I. officials who exchanged texts disparaging Mr. Trump during the campaign. The officials, Peter Strzok and Lisa Page, were involved in both the Clinton and Russia investigations, leading Mr. Trump’s supporters to suspect a conspiracy against him. Many of those text messages have been released, but the inspector general cites a previously undisclosed message in which Mr. Strzok says the F.B.I. “will stop” Mr. Trump, according to two of the officials.
The inspector general said that, because of his views, Mr. Strzok may have improperly prioritized the Russia investigation over the Clinton investigation during the final weeks of the campaign. The F.B.I. officials “brought discredit” to themselves and sowed public doubt about the investigation. But the report did not cite evidence that Mr. Strzok had acted improperly or influenced the outcome of the investigation, the officials said.
“Our review did not find evidence to connect the political views expressed in these messages to the specific investigative decisions that we reviewed,” the report said, according to the official who read it to The Times.
The findings sharply criticize the judgment of Mr. Comey, who injected the F.B.I. into presidential politics in ways not seen since at least the Watergate era.
Mr. Comey held a news conference in July 2016 to announce that he was recommending no charges against Mrs. Clinton and to publicly chastise her email practices. It was highly unorthodox; the Justice Department, not the F.B.I., makes charging decisions. And officials have been reprimanded for injecting their opinions into legal conclusions. Mr. Comey withheld his plans for a public statement from his bosses at the Justice Department.
“It was extraordinary and insubordinate for Comey to do so,” the inspector general wrote, “and we found none of his reasons to a persuasive basis for deviating from well-established department policies in a way intentionally designed to avoid supervision by department leadership.”
Then in late October, over the objection of top Justice Department officials, Mr. Comey sent a letter to Congress disclosing that agents were scrutinizing new evidence in the Clinton case. That evidence did not change the outcome of the inquiry, but Mrs. Clinton and many of her supporters blame Mr. Comey’s late disclosure for her defeat.
Mr. Comey has defended his actions, saying he would have faced criticism for any decision, so he opted to be transparent. F.B.I. officials have acknowledged that they made those decisions in part because they assumed Mrs. Clinton would win, and they worried about appearing to conceal information to help her.
The inspector general’s report serves as an official book end to Mr. Comey’s three-and-a-half-year tenure as director. He cultivated a reputation for fierce independence and supreme self-confidence. Those traits were both assets and vulnerabilities. Agents widely saw him as a strong leader.
But Mr. Comey believed that he was the only one who could steer the F.B.I. through the political winds of the Clinton case, and that left him alone to answer for the bureau’s actions.
Officially at least, Mr. Comey’s handling of the Clinton case cost him his job. As justification for firing him last year, the White House pointed to a Justice Department memo that criticized many of the same actions now highlighted by the inspector general. In that regard, the inspector general would seem to underscore the stated reason for Mr. Comey’s dismissal.
But Mr. Trump has muddied this issue. Within hours of the firing, he undercut his own staff and said that he had planned to fire Mr. Comey even before the Justice Department made its recommendation. He said he had been thinking about the Russia investigation when he fired Mr. Comey. His lawyer added that Mr. Comey was fired for refusing to publicly exonerate Mr. Trump in the Russia case.
And though Mr. Comey’s public actions were seen by Mrs. Clinton’s campaign as deeply harmful, the president has embraced a theory that the F.B.I. actually conspired to help her.
The result of these positions is that what might have been a vindicating report for Mr. Trump no longer fits neatly into his theories about Mr. Comey, Mrs. Clinton or the F.B.I. in general. Nevertheless, the report gives Mr. Trump plenty of ammunition for his continued broadsides against the bureau. The newly discovered text message, in particular, bolsters his argument that people inside the F.B.I. opposed him.
The inspector general is separately reviewing some aspects of the Russia investigation, including Mr. Trump’s theory — backed up by no evidence — that the F.B.I. spied on his campaign for political purposes. Those matters were not covered in the report to be released Thursday.
The inspector general’s investigation has already led to the firing of one top F.B.I. official, the former deputy director Andrew G. McCabe. Mr. Horowitz issued a report in March that said Mr. McCabe had been dishonest about his contacts with the news media about Mrs. Clinton.
Adam Goldman and Katie Benner contributed reporting.