The nation's largest group lobbying for repeal of “Don't Ask, Don't Tell” is advising gay troops not to answer a Pentagon survey on the policy.

The Servicemembers Legal Defense Network (SLDN) warned Thursday that gay and lesbian personnel could be accidentally outed by answering the survey, which could lead to a discharge.

“There is no guarantee of privacy,” the group said, “and [the] DoD has not agreed to provide immunity to service members whose privacy may be inadvertently violated or who inadvertently outs himself or herself.”

The Department of Defense announced Wednesday that 400,000 servicemembers will receive the survey that directs participants to a secure website where they are asked to answer roughly 90 questions, including whether or not the policy that bans openly gay service should be lifted.

Half of the surveys were sent to active-duty personnel, and half were sent to reserve troops. Another 150,000 surveys will be mailed to military spouses before the end of the month.

The survey is part of the military's comprehensive review of “Don't Ask, Don't Tell,” the law approved by Congress and signed by President Bill Clinton in 1993.

The review was ordered by Defense Secretary Robert Gates and is expected to be completed by December 1. Army General Carter F. Ham, commander of the U.S. Army Europe, and Jen Johnson, the Pentagon's top lawyer, head the review panel.

Under a deal brokered between gay rights groups and lawmakers, the assessment will continue even as Congress debates whether to repeal the law. Republicans have voiced concern over repealing the law before the review is complete. House members voted in favor of repeal in May, while senators are expected to take up the issue this month. The legislation – under the terms of the deal – gives the military and President Barack Obama final say on the specifics of repeal and would not be implemented until after the military completes its review.

In announcing the Pentagon had begun surveying troops on the policy, Ham said it is “vitally important that servicemembers continue to be open and frank and totally honest with us in their feedback.”

But SLDN Executive Director Aubrey Sarvis cautioned gay troops on completing the survey, saying they should “only do so in a manner that does not reveal sexual orientation.”