WASHINGTON -- Marine Commandant Robert Neller vowed “we’ll take action to correct this stain on our Marine Corps,” at a hearing of the Senate Armed Services Committee, promising to overhaul the culture which gave rise to websites which shared nude photos of female Marines.

Gen. Robert Neller testifies in a Senate hearing Tuesday CBS News

Neller’s statement did not impress New Hampshire Sen. Jeanne Shaheen.

“Why should we believe it’s going to be different this time than it’s been in the past?” Shaheen asked.

“Is it going to be different? It’s got to be different,” Neller said.

“When you say to us it’s got to be different, that rings hollow,” said Sen. Kirsten Gillibrand of New York.

Gillibrand pointed to a letter sent to the previous Marine commandant in 2013, identifying websites which denigrated female Marines.

“Who is being held accountable for doing nothing since 2013? Who? Which commander?” Gillibrand asked.

“I don’t have a good answer for you. I’m not going to sit here and duck around this thing. I’m not. I’m responsible. I’m the commandant. I own this,” Neller said.

Neller has said he was not aware of these sites until this year when a former Marine turned journalist alerted him to Marines United, a Facebook page on which current and former Marines shared nude photos of women.

Erin Kirk-Cuomo CBS News

But Erin Kirk-Cuomo, who left the Corps in 2010, told CBS News female Marines were complaining about these sites even then.

“This is an ongoing issue. It’s not something new,” she said. “This is something that has been pervasive and has been going on for over a decade.”

Kirk-Cuomo believes it is part of a culture which begins with boot camp when women recruits are segregated from the men.

“This behavior is ingrained in Marine Corps culture simply because they as male Marines are told from the very beginning of training that females are inferior,” she said.

Neller testified that about 500 current and former Marines have been identified so far as having shared nude photos of female Marines over the internet.

And that’s just one site; Investigators have found at least 17 more sites containing thousands of photos.