Rear Adm. Brian L. Losey, head of the Naval Special Warfare Command, was found to have violated whistleblower protection laws, but he was not disciplined. (U.S. Navy )

A U.S. senator said Friday that he would block the nomination of the Navy’s second-ranking civilian leader until the service reconsiders its decision not to punish a prominent admiral accused of retaliating against several whistleblowers.

The move by Sen. Ron Wyden (D-Ore.) escalates the pressure on Navy leaders to take action against Rear Adm. Brian L. Losey, the commander in charge of the service’s SEAL teams and other elite units.

The Washington Post reported in October that the Navy was poised to promote Losey even though Pentagon investigators had determined that he illegally retaliated against staff members who he mistakenly suspected were whistleblowers.

Losey, a prominent figure in the military’s secretive Special Operations forces, once commanded SEAL Team 6, the clandestine unit known for killing terrorist targets such as Osama bin Laden. He now leads the Naval Special Warfare Command and previously served as a top military aide to the White House.

In a statement submitted to the Congressional Record, Wyden said he had placed a hold on the nomination of Janine Davidson, a former Pentagon official and Air Force pilot, to become the next Navy undersecretary.

Wyden said he didn’t have any concerns with Davidson herself but rather “with a larger matter concerning the Navy and its policies and practices with regard to retaliation against whistleblowers.” The lawmaker said he wanted “assurances” from the Navy that it would revisit the Losey case.

Late Friday, the Navy issued a statement defending its decision not to take action against Losey for his handling of the whistleblowers, but said that his pending promotion was under fresh review.

Wyden is among several lawmakers who have expressed concern over the Navy’s decision not to discipline Losey. He said he and seven other senators, whom he did not name, had asked the Pentagon in October for copies of the whistleblower investigative reports involving Losey. The reports were released this week.

The military’s whistleblower protection laws are relatively weak, and it is rare for violators to be punished. The Pentagon’s inspector general investigates more than 1,000 whistleblower cases a year but upholds fewer than 1 in 25 complaints.

Losey was investigated five times by the Defense Department’s inspector general after subordinates complained that he had wrongly fired, demoted or punished them during a fruitless hunt for a person who had anonymously reported him for a minor travel-policy violation.

After conducting separate, years-long investigations that involved more than 100 witnesses and 300,000 pages of email, the inspector general upheld complaints from three of the five staff members. In each of those cases, it recommended that the Navy take action against Losey for violating whistleblower protection laws, according to copies of the investigative reports obtained by The Post.

The Navy, however, dismissed those findings in October and decided not to discipline Losey, accepting his explanation that he had taken action against the staff members because they were poor performers, not suspected whistleblowers.

In the statement released late Friday, Rear Adm. Dawn Cutler, the Navy’s chief spokeswoman, said Navy leaders “thoroughly reviewed” the inspector general’s investigations but concluded in October that Losey’s actions were “not reprisals.”

That decision had appeared to clear the way for Losey to pin on a higher rank as a two-star admiral. He had been originally selected for promotion in 2011 and was confirmed by the Senate, though his advancement was placed on hold until the whistleblower investigations could be resolved.

Although the Navy officially absolved Losey of misconduct, Cutler said that the service was taking a fresh look at whether he still merited promotion.

“The process and the standard for determining an officer’s qualifications for promotion and for determining whether misconduct occurred are different,” she said. “The Navy uses the highest level of thoroughness and scrutiny in making promotion recommendations, and all relevant and appropriate information is reviewed.”