WASHINGTON — A top Interior Department official broke a federal ethics rule by improperly meeting with his former employer, a conservative research organization, to discuss the rollback of endangered species protections that the group had been pushing, the department’s internal watchdog said in a report published Tuesday.

The watchdog, the Interior Department’s inspector general, concluded that the official, Douglas W. Domenech, an assistant Interior secretary for the office with stewardship of the nation’s oceans and coasts, violated federal rules in April 2017 when he met with representatives of the Texas Public Policy Foundation, where he was working before he joined the Trump administration, creating the appearance of a conflict of interest.

A separate inspector general investigation made public Tuesday cleared the Interior secretary, David Bernhardt, of charges that he improperly tried to influence or delay a scientific report on the effects of pesticides on endangered species. The inspector general found that Mr. Bernhardt had intervened in the writing of the report, which likely delayed its publication and may have changed some of its content. But the investigation concluded that Mr. Bernhardt’s actions, which were first reported in a New York Times investigation, did not constitute an ethics violation and that none of his former lobbying clients would have been affected by the outcome of the report.

The Texas Public Policy Foundation, which has received substantial funding from Charles and David Koch, the billionaire brothers who have fought environmental regulations, has salted the Trump administration with many of its top officials, elevating its influence and prestige.