A top aide to President Trump has resigned amid allegations of abusive behavior from his two ex-wives.

Rob Porter, White House staff secretary, had been accused in multiple media reports published earlier in the week of choking and dragging his wives. Although White House aides had defended Porter in statements to the media, Porter submitted his resignation on Wednesday as scrutiny of his past relationships intensified.

"He is going to be leaving the White House. It won't be immediate," White House press secretary Sarah Sanders told reporters on Wednesday.

"Rob has been effective in his role as staff secretary, and the president and chief of staff has had full confidence" in his job performance, Sanders added. She read a statement from Porter that described the allegations as "outrageous."

"I will not further engage publicly with a coordinated smear campaign," Porter said in the statement Sanders read.

Porter is reported to be in a romantic relationship with White House communications director Hope Hicks. His last day in the West Wing has not yet been set, which Sanders described as an effort to ensure a "smooth transition" when he departs.

Sanders said in a statement released later Wednesday that the administration had performed a "thorough" background check on Porter, but she declined to specify what the White House knew of Porter's personal history, if anything. The Daily Mail had reported on Tuesday that the FBI interviewed both of Porter's ex-wives as part of the process of approving his security clearance, which he reportedly did not obtain.

"Consistent with the practice of past administrations, issues related to an individual's suitability are reviewed through a thorough and lengthy background check process. Background checks involve a complex investigation run by intelligence and law enforcement agencies," Sanders said in a statement. "As has always been our policy, we do not comment on security clearances. Rob Porter has been effective in his role as staff secretary. The president and chief of staff have full confidence in his abilities and his performance."