The Pentagon is expected to announce a 50 jump in sexual assault reports on Thursday when it releases its annual study of the problem amid continuing revelations of questionable behavior by military officers responsible for dealing with the issue.

The annual study was expected to show a 50 percent jump to about 5,000 reports of sexual assault in the military in the 2013 fiscal year that ended on September 30, congressional aides said, a figure in line with preliminary numbers released by the Pentagon in December.

By comparison, the Pentagon's Sexual Assault Prevention and Response office said 3,374 cases of sexual assault were reported in the 2012 fiscal year.

Sexual assault is a hugely underreported crime, and a separate military survey conducted in 2012 concluded there were some 26,000 sex crimes in the military that year, from rape to abusive sexual contact.

The survey is conducted every two years, so there will be no survey with the annual report this year to use as a basis for projecting total sex crimes in the services, congressional aides said.

The figures last year provoked outrage and led to a broad effort across the military to crack down on sex crimes and sexual misbehavior.

Congress took action to force the military to tighten its response to the problem, but it ultimately rejected a push by many lawmakers to take decisions about prosecution of sex crimes out of the hands of the victims' military commanders.

The release of this year's report comes amid continuing revelations about tolerance of the problem by some military leaders responsible for fighting it.

The Navy said last week it was investigating allegations of misconduct by Captain Gregory McWherter, the former commanding officer of the Blue Angels, the Navy's precision aerobatics flight squadron.

McWherter is accused of tolerating an inappropriate work environment in the Blue Angels two years ago, allowing or in some cases encouraging "lewd speech, inappropriate comments, and sexually explicit humor," the Navy said.

Major General Michael Harrison also was recently disciplined for failing to take appropriate action in response to sexual assault allegations while he was commander of U.S. Army forces in Japan. He had been suspended from the post last June when the allegations were made.

The new sexual assault figures and recent mishandling of some cases by military commanders are expected to prompt calls for Senator Kirsten Gillibrand, a New York Democrat, to renew her push to remove prosecution of the crime from the victims' chain of command.

Army General Martin Dempsey, the highest-ranking military officer, told defense bloggers earlier this month that the department had a limited window of opportunity to demonstrate it could deal with the sexual assault problem.

"If it occurs that after a period of very intense and renewed emphasis on this that we can't solve it, I‘m not going to fight it being taken away from us," the military's press service quoted him as saying.

(Reporting by David Alexander and Patricia Zengerle; Editing by Sofina Mirza-Reid)