WASHINGTON — Members of a House panel angry over the growing epidemic of sexual assaults in the military took a key step toward tackling the problem by passing legislation Wednesday that would strip commanding officers of their longstanding authority to unilaterally change or dismiss court-martial convictions in rape and assault cases.

Lawmakers believe the revision will lead to a cultural shift and encourage victims to step forward.

The legislation, which will be folded into a broader defense policy bill that the full House will consider in the coming weeks, also would impose harsher penalties on service members found guilty of sexual offenses by requiring that they be dismissed or dishonorably discharged.

The moves by the House Armed Services military personnel subcommittee reflect outrage on Capitol Hill over the poor results military leaders have achieved in their efforts to combat sexual assault in the ranks.

A Pentagon report released this month estimated that up to 26,000 military members may have been sexually assaulted last year, and that thousands of victims are unwilling to come forward despite new oversight and assistance programs aimed at curbing the crimes.

The report showed that the number of sexual assaults actually reported by members of the military rose 6 percent to 3,374 in 2012.

But a survey of personnel who were not required to reveal their identities showed the number of service members actually assaulted could be as high as 26,000.

That figure is an increase over the 19,000 estimated assaults in 2011.

Congress has repeatedly challenged the military to take more aggressive steps to curb sexual assault, but the new figures convinced lawmakers that military leaders have not done enough, and that swift legislative action is needed.

President Barack Obama has weighed in as well, declaring that he wants to eliminate the “scourge” of sexual assault.

The subcommittee’s vote came after a string of incidents that raised fresh doubts about the military’s commitment to tackling the problem.

The Army said Wednesday that a soldier is facing several charges after being accused of secretly photographing and videotaping women at the U.S. Military Academy at West Point, including in a bathroom.

Rep. Joe Wilson, R-S.C., the military personnel subcommittee chairman, said the proposed changes are significant and will give assault victims the confidence to report crimes.