But the inspector general found major errors, material omissions and unsupported statements about Mr. Page in the materials that went to the court. F.B.I. agents cherry-picked the evidence, telling the Justice Department information that made Mr. Page look suspicious and omitting material that cut the other way, and the department passed that misleading portrait onto the court.

To give just three examples:

First, when agents initially sought permission for the wiretap, F.B.I. officials scoured information from confidential informants and selectively presented portions that supported their suspicions that Mr. Page might be a conduit between Russia and the Trump campaign’s onetime chairman, Paul Manafort.

But officials did not disclose information that undercut that allegation — such as the fact that Mr. Page had told an informant in August 2016 that he “never met” or “said one word” to Mr. Manafort, who had never returned Mr. Page’s emails. Even if the investigators did not necessarily believe Mr. Page, the court should have been told what he had said.

Second, as the initial court order was nearing its expiration and law-enforcement officials prepared to ask the surveillance court to renew it, the F.B.I. had uncovered information that cast doubt on some of its original assertions. But law enforcement officials never reported that new information to the court.

Specifically, the application included allegations about Mr. Page contained in a dossier compiled by Christopher Steele, a former British intelligence agent whose research was funded by Democrats. In January 2017, the F.B.I. interviewed Mr. Steele’s own primary source, and he contradicted what Mr. Steele had written in the dossier.

The source for Mr. Steele may, of course, have been lying. But either way, officials should have flagged the disconnect for the court. Instead, the F.B.I. reported that its agents had met with the source to “further corroborate” the dossier and found him to be “truthful and cooperative,” leaving a misleading impression in renewal applications.

Finally, the report stressed Mr. Page’s long history of meeting with Russian intelligence officials. But he had also said that he had a relationship with the C.I.A., and it turns out that he had for years told the agency about those meetings — including one that was cited in the wiretap application as a reason to be suspicious of him.