WASHINGTON - In the vast majority of military sexual assault cases - as many as 22,000 in 2012 - the victim chooses not to report the attack or unwanted sexual contact.

Troubling new numbers estimate that up to 26,000 military members may have been sexually assaulted last year, according to a massive report the Pentagon released on Tuesday.

Of those, fewer than 3,400 reported the incident, and nearly 800 of them simply sought help but declined to file complaints against their alleged attackers.

The statistics emerged against a backdrop of scandals, including an ongoing investigation into more than 30 Air Force instructors for assaults on trainees at a Texas base. And the report comes just days after the Air Force's head of sexual assault prevention was arrested on charges of groping a woman in a Northern Virginia parking lot.

Congressional outrage over these incidents and a decision by an Air Force officer to overturn a jury's guilty verdict in a sexual assault case is producing sweeping legislation that two House members introduced on Wednesday.

Reps. Mike Turner, R-Ohio, and Niki Tsongas, D-Mass., are proposing stripping an officer's authority to change or dismiss a court-martial conviction in major cases, such as sexual assault. Their bill would also require that an individual found guilty of rape, sexual assault, forcible sodomy and an attempt to commit any of those offenses be either dismissed or dishonorably discharged.

"Our effort is to try to get some standardized guidelines as to punishment for sexual assault convictions, taking it out of the chain of command and instilling some standards that can have a preventive effect on perpetrators," Turner said Wednesday.

Separately, Senate Majority Leader Harry Reid, D-Nev., sent a letter to the leaders of the Senate Armed Services Committee pressing them to include a provision in the defense policy bill stripping commanders of the authority to overturn convictions in sexual assault cases.

"We must hold the perpetrators of these horrible acts accountable. Failure to do so would be a betrayal of our national values and of the men and women serving in our military," Reid wrote Sens. Carl Levin, D-Mich., and Jim Inhofe, R-Okla.

In a sharp rebuke Tuesday, President Obama said he has no tolerance for the problem and said he had talked to Defense Secretary Chuck Hagel about it. He said any military member found guilty of sexual assault should be held accountable, prosecuted and fired.

"I don't want just more speeches or awareness programs or training, or ultimately folks look the other way," the president said. "We're going to have to not just step up our game, we have to exponentially step up our game to go after this hard."

Hagel later gave a grim assessment, saying the military "may be nearing a stage where the frequency of this crime and the perception that there is tolerance of it could very well undermine our ability to effectively carry out the mission and to recruit and retain the good people we need."