WASHINGTON — An inspector general uncovered pervasive problems in the F.B.I.’s preparation of wiretap applications, according to a memo released Tuesday about an audit that grew out of a damning report last year about errors and omissions in applications to target a former Trump campaign adviser during the Russia investigation.

The follow-up audit of unrelated cases by the Justice Department’s independent watchdog, Michael E. Horowitz, revealed a broader pattern of sloppiness by the F.B.I. in seeking permission to use powerful tools to eavesdrop on American soil in national security cases. It comes at a time when Congress is debating new limits on the Foreign Intelligence Surveillance Act, or FISA.

The finding of systemic incompetence is devastating for the F.B.I. But in the Trump era, the discovery is leavened by an unusual side benefit for the bureau: It undercuts the narrative fostered by President Trump and his supporters that the botching of applications to surveil his campaign adviser Carter Page is evidence that the F.B.I. engaged in a politically biased conspiracy.

Mr. Horowitz’s investigators reviewed so-called Woods files, where the F.B.I. is supposed to catalog supporting documentation for factual claims in a FISA application, in a random sample of 29 requests to wiretap someone as part of a terrorism or espionage investigation under FISA. They found problems with all 29.