The report, produced by the Department of Defense inspector general, concerns Rep. Ronny Jackson, who, it claims, made "sexual and denigrating comments" about a female subordinate, drank alcohol and took Ambien in ways that made colleagues question if he could provide care.
CNN first obtained the report, which was released on Wednesday.
Mr Jackson, a Texas Republican on the House Armed Services subcommittee that oversees military personnel, said the report was politically motivated in a statement. He claimed the inspector general "resurrected" old allegations against him. He said the report was meant to shame him for refusing to "turn my back on President Trump".
He rejected "any allegation that I consumed alcohol while on duty."
Investigators who prepared the report interviewed 78 witnesses and examined a trove of White House documents, and determined that the congressman disrespected his subordinates, used alcohol inappropriately on two occasions, and used sleeping pills during an overseas trip that made his colleagues question his ability to provide medical care to the president and others.
The witnesses has numerous disparaging comments to offer about Mr Jackson's leadership.
"Many of these witnesses described RDML Jackson's behaviour with words and phrases such as 'meltdowns,' 'yells' for no reason,' 'rages,' 'tantrums,' 'lashes out,' and 'aggressive'. These witnesses also described RDML Jackson's leadership style with terms such as 'tyrant,' 'dictator,' 'control freak,' 'hallmarks of fear and intimidation,' 'crappy manager,' and 'not a leader at all,'" the report said.
Mr Jackson - who began his role in the White House under former President Barack Obama - allegedly became intoxicated and made inappropriate comments about a female subordinate while on a presidential trip to Manila in 2014.
According to a witness, Mr Jackson reportedly began drinking in the hotel's lobby, then entered a car with a drink in hand "to go out on the town”.
Once he returned to the hotel, another witness claimed they saw him pounding on the door of a female subordinate. When she opened her door, he told her "I need you" and told her "I need you to come to my room."
Other witnesses to the scene said Mr Jackson made comments about the subordinate's breasts and buttocks during another 2014 trip to Asia.
"Witness 1, a medical subordinate, told us that during the Asia trip, before arriving in Manila, RDML Jackson told him a female medical subordinate (Manila Witness 2), who was also on the trip, had 'great t**s,' and 'what a nice a**,' and that RDML Jackson also told Manila Witness 1 that he would 'like to see more of her tattoos,'" the report said.
Only 13 of the 60 witnesses the Defense Department interviewed about Mr Jackson's leadership had anything positive to say about him. Thirty-eight said he displayed unprofessional behaviour, poor treatment of subordinates and intimidation while leading, with one claming Mr Jackson "established a workplace where fear and intimidation were kind of the hallmarks of him, his command, and control of his subordinates".
Mr Jackson claimed that the report was a Democrat-run smear campaign.
"Democrats are using this report to repeat and rehash untrue attacks on my integrity. I'm proud of the work environment I fostered under three different Presidents of both parties; I take my professional responsibility with respect to prescription drug practices seriously; and I flat out reject any allegation that I consumed alcohol while on duty," Mr Jackson said. "My entire professional life has been defined by duty and service. I've honourably served my country in the U.S. Navy, served patients who trusted me with their care, served three Presidents in the White House, and now I serve the people of Texas' 13th District in Congress. I have not and will not ever conduct myself in a way that undermines the sincerity with which I take my oath to my country or my constituents."