The Reagan administration's penchant for "private-sector" advice has touched off another skirmish, this one involving Interior Secretary Watt and his favorite sparring partners, the environmentalists.

Last summer, Watt set up a group called Protect Our Wetlands and Duck Resources (POWDR), with a membership composed largely of private landowners and corporate officials, to help him find ways to preserve the habitats of migratory birds. "In order to make this a successful program as quickly as possible, we are going to work outside normal government channels," Watt told the group's invited members. "This will not be a government-sponsored program. It will be an effort by those of us concerned enough to dedicate our time and effort to preserving wetlands and migratory bird habitat."

The Environmental Defense Fund, which has been dedicating time and effort to that cause for years, wasn't invited to sit on Watt's new panel -- to no one's great surprise, considering the defense fund has been nipping at Watt's heels since the day he took office. But the fund definitely doesn't like being left in the dark.

EDF attorney Michael J. Bean told Watt in a recent letter that, government-sponsored or not, the POWDR panel is expected "to give advice and counsel" to the Interior secretary, Congress and the Migratory Bird Commission, and it should be conducting business in the open, in accordance with the Federal Advisory Committee Act.

Interior disagrees. Department spokesman Douglas Baldwin described the private-sector group as "a group of folks in a position to do something, and they're doing things." As for the environmentalists, "All they've done is snipe at us in the most vicious partisan way possible."

The question of whether POWDR goes public is now in the hands of the General Services Administration, which is responsible for interpreting the requirements of the advisory committee act. GSA, which hadn't heard of POWDR until the environmentalists' complaint came in, has arranged a meeting with Interior officials later this month. Stay tuned.