Mr. Flynn has repeatedly denied any wrongdoing.

After Mr. Berry issued his report, Mr. Flynn’s lawyer, Barry Coburn, acknowledged, according to The Associated Press, that Mr. Flynn’s actions did not reflect “perfect judgment in every instance.” But Mr. Coburn said Mr. Flynn’s actions had not been illegal and that there was “not a shred of evidence that they were undertaken for any improper purpose.”

In his May report and one in March, Mr. Berry said the ethical violations occurred in 2010 and 2011, when Mr. Flynn was a staff lawyer for a Republican member of the board, Brian Hayes. Mr. Flynn joined the board in 2003 as chief counsel to Mr. Schaumber, then an N.L.R.B. member.

Mr. Berry found that Mr. Flynn had leaked information to Mr. Schaumber and to Peter Kirsanow, a former Republican N.L.R.B. member who was serving as outside counsel for the National Association of Manufacturers. The Romney campaign said Mr. Schaumber had stepped down from his advisory position in December, which was after Mr. Berry’s investigation began. The inspector general’s reports did not accuse Mr. Schaumber of using the material he had received from Mr. Flynn to help the Romney campaign.

In one instance, Mr. Berry found that Mr. Flynn had secretly helped Mr. Schaumber write an opinion column that denounced an N.L.R.B. decision that favored labor unions. Mr. Berry called that action by Mr. Flynn “an abuse of his discretion.”

The Flynn case has been referred to the Justice Department for investigation and to the Federal Office of Special Counsel, which is looking into possible violations of the Hatch Act, which bars federal employees from participating in partisan political activity.