WASHINGTON — Sexual misconduct remains a destructive force in the armed forces and military communities, a U.S. senator said Monday in a new report that urges Congress to take more aggressive steps to end sex crimes in the ranks.

Sen. Kirsten Gillibrand, D-N.Y., examined files from 329 sexual assault cases that occurred in 2014 at bases in the United States. She said she found a "troubling command culture" that seems to favor closing cases over pursuing justice and leaves victims vulnerable to retaliation.

"The military justice system is still dysfunctional, the problem of sexual assault is still pervasive and survivors still don't believe they will get justice," said Gillibrand, the top Democrat on the Senate Armed Services personnel subcommittee.

The Defense Department did not immediately respond to a request for comment.

Gillibrand's report could strike nerves on Capitol Hill and at the Pentagon. Many lawmakers and senior U.S. military leaders say strides have been made over the past three years toward curbing sex crimes and punishing offenders. Congress has ordered numerous changes to the military justice system, they say, giving victims the confidence to step forward and report offenses.

The department said earlier this month that the number of reported sexual assaults involving active-duty service members dipped just slightly in 2015 compared to the previous year.

But Gillibrand said significant progress won't be made without more extensive reforms. She said the records reveal how sexual violence affects not only service members. Nearly a third of the cases involved civilian women, children and military spouses, the report said.

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The report is being released ahead of the Senate's consideration of the annual defense policy bill. Gillibrand is pushing to include in the bill a measure that she said targets "the bias and inherent conflicts of interest" that exist because of the way the military decides whether to prosecute sexual assault cases. That decision-making power is currently held by a small number of high-ranking officers. Gillibrand's proposal would give that authority instead to seasoned, independent military trial lawyers.

A bipartisan group of senators led by Gillibrand and Sen. Charles Grassley, R-Iowa, are scheduled to hold a news conference Tuesday to call on the Senate to pass her proposal. It was first introduced in the spring of 2013 and has won the backing of at least 50 senators. But the legislation has twice failed on the Senate floor to meet a 60-vote filibuster threshold. Grassley is the chairman of the Senate Judiciary Committee.

Critics of Gillibrand's bill said commanders are essential to maintaining good order and discipline in the ranks. Removing them would mean fewer sex offenders will be caught and convicted, they said.

The U.S. Military Academy Noncommissioned Officers led a run at West Point in 2013 to reaffirm their commitment to preventing sexual harassment and sexual assault in support of the U.S. Army SHARP program.

Photo Credit: Army via USMA PAO

Yet Gillibrand said there were several 2014 cases that failed to move forward even after military investigators found probable cause to do so. In one, an investigation determined that an enlisted service member sexually assaulted a woman while he used physical force to subdue her. But the command chose not court-martial him. He was found guilty of battery, given 45 days extra duty and reduced in rank.

"The case files suggest a continued large-scale systemic failure and an ingrained culture that protects the accused and ostracizes the survivor at the expense of the public and our service members' safety," according to Gillibrand's report.

There were no examples among the 329 cases of action being taken against anyone who retaliated against a person who made a sexual assault claim. Gillibrand said she specifically asked for information about prosecutions for retaliation and the absence of any is concerning.

In December 2014, a RAND survey initially said that more than 60 percent of sexual assault victims believed they had faced a form of retaliation from commanders or peers. The department reduced the estimate this year to nearly 38 percent after officials concluded that the survey questions may have inadvertently included actions by commanders seeking to protect the victim or other social practices that were not designed to deter a victim from pressing forward with criminal proceedings.

"Nevertheless, we have seen scant to no evidence that retaliation cases are being pursued anywhere in the services," Gillibrand said.

Gillibrand said the Pentagon resisted providing the case files and only relented after the Senate Armed Services chairman, Republican John McCain of Arizona, intervened.

Gillibrand released a similar study a year ago that examined files for 2013 cases from the same four bases: the Army's Fort Hood in Texas, Naval Station Norfolk in Virginia, the Marine Corps' Camp Pendleton in California and Wright-Patterson Air Force Base in Ohio.

The case files the Defense Department provided are heavily blacked out and often incomplete, according to Gillibrand. An AP investigation published in November found a lack of transparency in the military justice system that makes it difficult for the public to know the details of cases that end in convictions.