The estimated number of military personnel victimized by sexual assault and related crimes has surged by about 35 percent over the past two years, the Pentagon reported Tuesday, as the White House and lawmakers expressed anger with the military’s handling of the problem.

The sobering statistics, along with several recent sexual-abuse scandals in the armed services, prompted President Obama to bluntly warn the Defense Department that he expected its leaders to take tougher action against sex offenders and redouble their efforts to prevent such crimes.

“The bottom line is, I have no tolerance for this,” Obama told reporters. “If we find out somebody’s engaging in this stuff, they’ve got to be held accountable, prosecuted, stripped of their positions, court-martialed, fired, dishonorably discharged — period.”

Members of Congress likewise signaled a loss of patience, introducing a flurry of bills in recent days that would revise military law to bolster the prosecution of sexual-assault cases and give more legal support to victims.

Senators also grilled Air Force leaders about the weekend arrest of the Air Force’s chief for sexual-assault prevention on charges that he groped and attacked a woman in Northern Virginia. Some lawmakers called it an example of a cultural problem within the military that commanders have been unable to change.

Lt. Col. Jeffrey Krusinski, an Air Force officer who led the branch's Sexual Assault Prevention and Response unit, has been charged with groping a woman in a parking lot. (AP/Arlington County Police Department)

“They’re failing in this regard, sir,” Sen. Kirsten Gillibrand (D-N.Y.) sternly told Air Force Secretary Michael Donley during a hearing of the Senate Armed Services Committee. “If the man in charge for the Air Force in preventing sexual assault is being alleged to have committed a sexual assault this weekend, obviously there’s a failing in training and understanding of what sexual assault is and how corrosive and damaging it is.”

Other lawmakers said they were upset to learn about two cases in which Air Force generals granted clemency to convicted sex offenders, adding that the decisions would discourage other victims from reporting rape or sexual abuse.

“That is the crux of the problem here, because if a victim does not believe that the system is capable of believing her, there’s no point in risking your entire career,” said Sen. Claire McCaskill (D-Mo.), another member of the Armed Services Committee.

Obama said he had instructed Defense Secretary Chuck Hagel “to step up our game exponentially ” to prevent sex crimes in the military and hold offenders accountable. “For those who are in uniform who’ve experienced sexual assault, I want them to hear directly from their commander in chief that I’ve got their backs,” he added.

The Pentagon, using anonymous surveys and sampling research, estimated that 26,000 personnel experienced “unwanted sexual contact” last year, up from about 19,300 in 2010, according to an ongoing Defense Department study.

Military officials said they are concerned that most victims are reluctant to press charges or formally report sexual assault because they fear retaliation or ostracism from their units. The Pentagon recorded 3,374 sexual-assault reports last year, compared with 3,192 in 2011.

In both years, fewer than one in 10 cases ended with a sex-assault conviction at court-martial. The vast majority resulted in minor, administrative punishments or were dismissed altogether, the Pentagon study found.

In a briefing with reporters, Hagel warned that the military was being fundamentally undermined by the rising prevalence of sexual assault. He announced a series of new programs designed to assist victims and hold commanders accountable for how seriously they take the issue.

“This department 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,” he said. “That is unacceptable to me and the leaders of this institution.”

But Hagel and other military leaders said they opposed efforts by some lawmakers to revamp the military code of justice so that prosecutors and judges — and not commanding officers — would be solely responsible for handling sexual-assault cases.

Hagel, Donley and Gen. Mark Welsh, the Air Force chief of staff, said that it was important for commanders to retain that authority.

“That would just weaken the system,” Hagel said. He added, however, that he would support legislation to curtail the ability of commanders to grant clemency to convicted offenders.

Welsh told senators that military lawyers would request jurisdiction in the case involving Lt. Col. Jeffrey Krusinski, the chief of the Air Force’s sexual assault prevention branch. Krusinski was arrested by Arlington County police early Sunday and charged with sexual battery.

Police said Krusinski was drunk about 12:30 a.m. when he approached a woman in a Crystal City parking lot and grabbed her breasts and buttocks. The woman fended off her assailant, but “then he attempted to attack her again, and she called 911,” said Dustin Sternbeck, an Arlington police spokesman.

Efforts to reach Krusinski by e-mail and phone Tuesday morning were not successful.

Welsh said that he was “appalled” by the arrest and that “it is unacceptable that this occurs anytime or anywhere in our Air Force.” He said that Arlington prosecutors would make a final decision about whether to grant jurisdiction in the case to the military.

Krusinski is scheduled for arraignment Thursday in Arlington. His booking photo depicted him with a cut under his left eye and contusions on his upper lip. Police said the victim did not know her attacker.

The Air Force has acknowledged that it is struggling to contain “a cancer” of sexual assault in the ranks. The service’s leadership has faced particular scrutiny from lawmakers and advocacy groups over its handling of sex-crime cases, including the rape and assault of dozens of recruits by basic-training instructors at Lackland Air Force Base in Texas.

“Within the Air Force, it has to become unacceptable culturally,” Sen. Angus King (I-Maine) told Welsh and Donley. “The culture is what you have to deal with.”

Alice Crites, Ernesto Londoño and Ed O’Keefe contributed to this report.