The House Ethics Committee, which has been investigating allegations that Representative Matt Gaetz engaged in sexual misconduct and illicit drug use, was prepared to vote to release a highly critical report about Mr. Gaetz on Friday, according to a Republican official familiar with the matter. The release would have come two days after President-elect Donald J. Trump selected Mr. Gaetz to be attorney general.

Mr. Gaetz, a Florida Republican, abruptly resigned from his House seat late Wednesday, effectively ending the ethics investigation that has hung over his head for years.

Mr. Gaetz, the official said, had repeatedly offered combative replies to questions posed by the committee, effectively delaying the fact-finding process for months. The publication of the committee’s findings was additionally delayed, the official said, because of a House rule that forbids releasing a negative report close to an election. The official spoke on condition of anonymity to discuss a sensitive investigation.

Now, with Mr. Gaetz’s departure from Congress, the committee no longer has jurisdiction to investigate him. It was not immediately clear whether it would still release its findings. Tom Rust, the chief counsel and staff director for the panel, declined to comment.

The report’s expected release on Friday was reported earlier by Punchbowl News.

Republicans in Congress expressed shock at Mr. Gaetz’s selection to be attorney general. Mr. Gaetz, who led the successful effort last fall to oust Speaker Kevin McCarthy of California, is one of the most reviled members of his conference.

For two years, the Justice Department looked into allegations that he had an inappropriate sexual relationship with a 17-year-old girl and possibly violated federal sex trafficking laws. The department closed its investigation last year without filing any charges against Mr. Gaetz.