WASHINGTON (AFP) - A US Army general who was Defence Secretary Ashton Carter's top military adviser used government credit cards at strip clubs, drank to excess and engaged in behaviour unbecoming an officer, says a probe released on Thursday (Oct 6).

Carter abruptly fired Major-General Ron Lewis from his prestigious post following a tour of Asia in November 2015, after allegations emerged about events on that and other trips.

The probe, carried out by the Inspector-General for the Department of Defence, documented a series of incidents dating back to April 2015, shortly after Carter was named as President Barack Obama's fourth defence chief.

Lewis is the latest US general to be fired for his conduct - two others lost their jobs this year for alleged improprieties.

On a trip to Seoul, Lewis racked up US$1,121 (S$1,530) on his government credit card at Candy Bar, a strip joint in the Hooker Hill area of Seoul's Itaewon district, the report states.

The club was off-limits to US military personnel because of its association with illicit activities, investigators wrote, noting Lewis had "received some form of services or benefits from those (credit card) transactions."

Lewis later said the charges were fraudulently put on his card, but investigators disputed those claims and said Lewis had made a false official written statement.

On a subsequent trip to Rome, Lewis visited the Cica Cica Boom club, drank to "more than moderation" for three hours, then brought a female club worker to a swish hotel - the same one Carter was staying at.

There, Lewis woke up a subordinate and told him to give him his government credit card to pay a US$1,755 bill from the club, after his personal debit card didn't work. He then went back to the club with the woman.

Investigators describe a series of other incidents, including a night in Hawaii in November at the end of the Asia trip.

Lewis allegedly drank alcohol with an enlisted service member and "backed her into a wall and caused her to believe he wanted some kind of physical contact."

The report notes that Lewis, who was not reachable for comment, denied several of the allegations.

The Inspector-General has turned the investigation over to the Army, which will decide on whether disciplinary actions and what rank Lewis will hold when he leaves the service.

Lewis, a former attack helicopter pilot, served in Iraq and Afghanistan and was briefly a three-star general while he worked with Carter.

Because he'd not held that rank for long, he dropped back to two stars after he was fired.

"I expect the highest possible standards of conduct from the men and women in this department, particularly from those serving in the most senior positions," Carter said in a statement.

"There is no exception."