Sexual assaults in the US military are a growing epidemic across the services and thousands of victims are still unwilling to come forward despite a slew of new oversight and assistance programs, according to a new Pentagon report.

Troubling new numbers estimate that up to 26,000 military members may have been sexually assaulted last year, according to survey results released on Tuesday.

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. And it follows a heated debate over whether commanders should be stripped of the authority to overturn military jury verdicts, such as one officer did in a recent sexual assault conviction.

The documents show 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 many as 26,000, but they never reported the incidents, officials said Tuesday.

‘Persistent problem’

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

The statistics highlight the dismal results that military leaders have achieved in their drive to change the culture within the ranks, even as the services redoubled efforts to launch new programs to assist the victims, encourage reporting and increase commanders' vigilance.

While the latest cases involve Air Force members, the problem extends across all the military services.

According to Pentagon documents, the key conclusion of the report is that "sexual assault is a persistent problem in the military and remains vastly underreported."

The report says that of the 1.4 million active duty personnel, 6.1 percent of active duty women - or 12,100 - say they experienced unwanted sexual contact in 2012, a sharp increase over the 8,600 who said that in 2010.

For men, the number increased from 10,700 to 13,900. A majority of the offenders were military members or Defense Department civilians or contractors, the report said.

In a sharp rebuke on Tuesday, President Barack Obama said he has no tolerance for the problem and that he had talked to Defence 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."