The Navy has denied promotion to the admiral in charge of its elite SEAL teams, effectively ending his military career, after multiple investigations found that he had retaliated against whistleblowers.

Officials said Navy Secretary Ray Mabus, under pressure from Congress, decided this week to reject Rear Adm. Brian L. Losey’s pending promotion to become a two-star admiral. Lawmakers had threatened to hold up nominations of other high-ranking Navy officials if they didn’t take action against the admiral, a prominent figure in the military’s secretive Special Operations forces.

The Washington Post reported in October that the Navy was poised to promote Losey despite findings from Pentagon investigators that he illegally demoted or punished three subordinates during a vengeful but fruitless hunt for an anonymous whistleblower who had reported him for a minor travel-policy infraction.

Navy leaders began reconsidering Losey’s status in December after Sen. Ron Wyden (D-Ore.) blocked the nomination of Janine Davidson, a former senior Pentagon official, to become the Navy’s second-ranking civilian leader. Wyden said he didn’t have any problem with Davidson herself, but wanted to force the Navy to revisit Losey’s case, adding that promoting him would send a message that retaliating against whistleblowers was acceptable.

Several other lawmakers pressured the Navy as well. In January, Sens. John McCain (R-Ariz.) and Jack Reed (D-R.I.), the chairman and ranking Democrat on the Senate Armed Services Committee, sent a joint letter to Mabus saying they had “deep reservations” about Losey’s pending promotion.

Rear Adm. Dawn Cutler, the Navy’s chief spokeswoman, confirmed that Losey’s promotion had been nixed “after further consideration” but lauded the SEAL’s long career in the military.

“The failure to promote does not diminish the achievements of a lifetime of service,” she said in a statement. “While the full scope of his service may never be known, his brilliant leadership of special operators in the world’s most challenging operational environments…reflected his incredible talent, energy, and devotion to mission. There are few in this country whose contributions to national security have been more significant.”

A combat veteran who has served in Iraq, Afghanistan, Panama, Bosnia and Somalia, Losey once commanded SEAL Team 6, the clandestine unit known for killing terrorist targets such as Osama bin Laden. He also once worked as a top military aide in the White House.

Wyden said he had been informed by the Navy this week that Losey will not be promoted. As a result, he said, he would remove his hold on Davidson’s nomination and support her confirmation to become the Navy’s new undersecretary.

“One of the pillars of our system of government is the rule of law; a principle that applies no less to our military and to the vital principle of civilian control over the military,” Wyden said in a statement. “It is illegal to retaliate against whistleblowers, whether civilian or military.”

Despite the pressure from Congress, a promotion board consisting of Navy admirals recently recommended in a majority vote that Losey be promoted anyway, according to a Pentagon official who spoke on condition of anonymity to discuss internal deliberations. The recommendation was overruled by Mabus, however, and Losey was notified Tuesday that his promotion had been rejected, the official said.

Losey did not respond to a request for comment placed through the Navy. He has previously denied wrongdoing, telling Pentagon investigators that his staff members were poor performers and that he had acted within his authority as a commander to demote or fire them.

The Navy announced on Feb. 29 that Losey’s tenure as leader of the Special Warfare Command would end this spring and that he would be replaced by Rear Adm. Timothy Szymanski, the assistant commander for operations at the Joint Special Operations Command at Fort Bragg. Navy officials said at the time that no decision had been made about Losey’s future and held out the possibility that he would receive another assignment.

On Thursday, Navy officials said Losey would submit an official request to retire.

Losey had originally been selected to become a two-star admiral in 2011 and was confirmed by the Senate. But his promotion was subsequently placed on hold after the whistleblowers filed complaints in 2012.

After conducting separate, years-long investigations that involved more than 100 witnesses and 300,000 pages of email, the Defense Department Inspector General upheld complaints from three of five staff members who asserted that Losey had illegally retaliated against them.