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

Senator Kirsten Gillibrand, Democrat of New York, 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 US 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 with 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.

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.