Pentagon investigating White House doctor who withdrew his nomination as Trump's VA secretary Dr. Ronny Jackson has denied allegations such as excessive drinking.

The Pentagon's Office of the Inspector General has begun an investigation into allegations related to Navy Rear Adm. Ronny Jackson, the White House doctor who withdrew his nomination to head the Department of Veterans Affairs amid allegations of unprofessional behavior.

"The DoD Office of Inspector General has initiated an investigation into allegations related to Rear Admiral (Lower Half) Ronny L. Jackson," Bruce Anderson, a spokesman for the inspector general of the U.S. Department of Defense, said.

A defense official said the investigation had been initiated recently.

News of the investigation comes more than a month after the Pentagon confirmed that the inspector general's office was reviewing whether an investigation or actions were warranted by the allegations.

Serving in the White House Medical Office for more than a dozen years, Dr. Jackson was President Donald Trump's surprise nominee to head the Department of Veterans Affairs.

But his nomination ran into immediate trouble as allegations surfaced about his alleged behavior.

Allegations were presented to the Senate Veterans Affairs Committee that accused Jackson of fostering a hostile work environment in the medical office, drinking to excess and improperly dispensing prescription drugs.

U.S. officials confirmed that the Navy initiated a command climate review in 2012 to look at the toxic work environment created in the White House Medical Office between Jackson and another top medical officer. But it found that the other medical officer was more to blame for the tense environment in the office.

Because of the political firestorm created by the allegations, Jackson withdrew his nomination April 26.

In his withdrawal statement, he labeled the allegations made against him as "completely false and fabricated."

"If they had any merit, I would not have been selected, promoted and entrusted to serve in such a sensitive and important role as physician to three presidents over the past 12 years," Jackson, 51, said.

Robert Wilkie, the Defense Department's undersecretary for personnel and readiness, has been nominated to be the next VA secretary.

Since his failed nomination, Jackson has continued serving in the White House Medical Office.