A gay group opposed to “Don't Ask, Don't Tell” says they've uncovered evidence that the Department of Defense has underreported discharges based on sexual orientation.

In a statement released Thursday, Servicemembers United, a group that represents gay and lesbian troops and veterans, said new figures obtained through a Freedom of Information Act request confirmed their suspicions about the official number of service members fired under “Don't Ask,” the 1993 law that bans gay troops from serving openly.

“These newly released data confirm what Servicemembers United has long suspected – that the official annual 'Don't Ask, Don't Tell' discharge numbers are underreported and incomplete,” Alexander Nicholson, executive director of the group, said.

The group says that the Department of Defense has confirmed that on three separate occasions it failed to include discharges from the National Guard or the Reserves in its official count.

The newly obtained document from the National Guard Bureau shows 630 discharges not included in the official count, pushing the 17-year total number of discharges to at least 14,055, up from 13,425.

“What's more is that there are even more discharges that have yet to be disclosed, and we're still working on obtaining those data,” Nicholson added.

Servicemembers United was among the groups lobbying for repeal of “Don't Ask” last week on Capitol Hill during Lobby Day 2010.