United States Senator Kirsten Gillibrand warned Monday that sex assaults are "vastly underreported" in the military, the AP reports.

Gillibrand reports that the Pentagon refused to give her all of the information she requested about sexual assaults on several major bases.

"I don't think the military is being honest about the problem," Gillibrand said in an interview.

The senator revealed that suspects received punishments that were too lenient or that their word was believed over the victim's in her analysis of 107 sexual assault cases. Only 11 cases resulted in conviction of a sex crime.

Female civilians are victims in more than half the cases. The senator's report found civilian women who live or work near military facilities and the spouses of service members are more vulnerable to being sexually assaulted.

Gillibrand found that some people stepped forward to accuse a suspect and instead of being brought to trial, investigator's decided to use administrative procedures to discharge a suspect who would have otherwise been convicted.

"It's frustrating because you look at the facts in these cases and you see witnesses willing to come forward, getting the medical exam and either eventually withdrawing their case or the investigators deciding that her testimony wasn't valid or believable," she said.

Yet, the Pentagon said Friday that there is a sharp decrease of sexual assault in the military, according to CNN. In the past two years, the percentage of military personnel who said they were victims of sexual assault dropped by 27 percent. 

According to Gillibrand, military commanders are not being tough on service members accused of sex crimes as the Pentagon stated.

To make sure that suspects are being convicted properly, the senator has legislation that would allow seasoned military attorneys with prosecutorial experience to judge cases. Yet, the Pentagon opposes her idea.

Senator Gillibrand is an outspoken advocate for an overhaul of the military justice system and critiques the Defense Department's efforts to curb sexual assaults.