The claims against Jackson include that he had wrecked a government vehicle after getting drunk at a Secret Service going-away party, had a "pattern" of handing out medication with no patient history, writing himself prescriptions and contributing to a hostile work environment with "a constant fear of reprisal".

The allegations were contained in a two-page document described by the Democratic staff of the Senate Veterans' Affairs Committee as a summary of interviews with 23 of Jackson's current and former colleagues.

Jackson, 50, told colleagues on Wednesday night that he had grown frustrated with the nomination process, according to two White House officials with knowledge of his deliberations.

He was a surprise nominee to succeed David Shulkin, an Obama-era holdover once lauded by Mr Trump, who was fired March 28.

Veteran advocates and many lawmakers had expressed concerns about Jackson's lack of management experience given he would lead an organisation of more than 360,000 employees, and some worried that he would capitulate to Mr Trump's goal of outsourcing more veteran services.

Apart from overseeing the White House medical staff, Jackson led a military trauma unit in Iraq, tending to troops who had suffered catastrophic wounds during one of the war's most violent stretches. He rose to prominence in January, after delivering a fawning assessment of Mr Trump's health.

Late last week, aides to Senator Jon Tester, the committee's ranking Democrat, received damaging information about Jackson's management of the White House medical office. They began interviewing his colleagues, many of them active-duty military officers, whose assessment of the admiral alarmed not only Senator Tester, but the committee's chairman, Republican Senator Johnny Isakson,  who agreed to postpone Jackson's confirmation hearing while lawmakers investigated the allegations.

The White House, which was criticized for failing to adequately vet Jackson's nomination, defended him until the end, saying that his record as a physician serving three presidents was unassailable, and demanding that he be allowed to defend himself during a confirmation hearing. But by Wednesday night, senators in both political parties doubted he could survive politically.

Since 2001, when the U.S. went to war in Afghanistan, VA has had seven secretaries. It's acting head is Robert Wilkie, who was moved into the role from another appointed position at the Defense Department.

Veterans advocacy groups said this week that politics have precluded the agency from effectively addressing the many challenges it faces as health care needs grow for Vietnam-era veterans and those who have served since 9/11.

Jackson planned to retire from the Navy to take VA job. Mr Trump has put him up for a promotion from to two-star admiral. That nomination remains pending with the Senate Armed Services Committee.

The Washington Post