WASHINGTON (AP) — An independent probe into the travel of Secretary of State Mike Pompeo’s wife has concluded that the trips with her husband on official business did not violate federal ethics rules.

But, in a report released Thursday, the department's acting inspector general, Matthew Klimow, also determined that the State Department did not secure proper written approval or documentation for six of Susan Pompeo’s eight trips covered by the investigation. In addition, the inspector general angrily rebutted accusations by Secretary Pompeo's aides that the investigation was a “waste of time.”

The investigation was begun under the leadership of inspector general Steve Linick, whom Pompeo fired in the spring after telling President Donald Trump he no longer had confidence in Linick. At the time, Linick had opened several investigations touching on Pompeo, and his dismissal was roundly criticized by ethics watchdogs and congressional Democrats.

The IG report was released just hours after the State Department took aim at the watchdog, Democratic members of Congress and media outlets for raising questions about Susan Pompeo’s travel and suggesting it may have been inappropriate. Susan Pompeo had attracted criticism for using government resources while accompanying her husband on diplomatic trips.

Although it found no evidence of misuse of taxpayer funds, Klimow said that, in response to a whistleblower's complaint, it had found documentation and approvals for only two of the eight trips Susan Pompeo took with her husband. It said those deficiencies should be corrected.

“OIG recommends that in order to ensure that the department has appropriate documentation for internal control and recordkeeping purposes, the Office of the Secretary seek and gain written approval for all representational travel, and that the Under Secretary for Management or other authorizing official document in writing the approval for all representational trips by any family members,” Klimow said.

In its response, the State Department agreed with the recommendation, but Under Secretary of State for Management Brian Bulatao and State Department Counselor Ulrich Brechbuhl, both longtime friends of Pompeo, slammed the inspector general for conducting the investigation in the first place.

Bulatao said he had verbally approved the trips for which the inspector general could not find documentation, while Brechbuhl slammed the IG for looking into an “administrative matter" that should have been dealt with differently.

“Given this work resulted only in a set of recommendations on purely administrative matters, department leadership wonders why the OIG wasted both time and resources writing a report,” Brechbuhl wrote. He said it would have been more appropriate for the matter to have been handled internally with no public notification.

The inspector general reacted icily to Brechbuhl's comment, saying it did not accurately reflect the role and work of an independent watchdog.

“This suggestion fundamentally misunderstands the independent role of OIG and our statutory oversight responsibilities,” Klimow said, noting that it is required to submit its findings to Congress and the public and that its role is fundamental to government transparency. "While the Department may view internal controls as mere ‘administrative matters’, they are mandated by law and are a key factor in improving accountability in achieving an entity’s mission.”

Secretary Pompeo has previously defended his wife's presence on his international trips by noting that she does work with diplomats’ families and is a “force multiplier” in boosting morale at overseas posts.

Previous secretaries of state had often brought their spouses along with them on official foreign travel, but since the late 1990s, it has been a rare because of family circumstances.

Neither Madeleine Albright nor Condoleezza Rice was married. Colin Powell's wife, Alma, preferred not to travel; Hillary Clinton's husband, Bill, a former president, presented security issues and never traveled with her; and John Kerry's wife, Teresa Heinz, suffered a brain injury early in his term, which left her unable to travel.