SEATTLE — The northern spotted owl, an icon of the Northwest’s environmental movement, was listed as threatened under the Endangered Species Act in 1990, but federal officials still have not bothered to come up with a plan for protecting it, said a lawsuit filed in U.S. District Court on Monday.

“They’ve been telling us for years they were going to do it,” said Alex Morgan, conservation director at the Seattle Audubon Society, which joined the Kittitas Audubon Society in filing the suit. “This is 15 years late.”

Joan Jewett, a spokeswoman for the U.S. Fish and Wildlife Service, acknowledged that federal officials never completed a final recovery plan for the Northern spotted owl. Part of the reason was that the compromise Northwest Forest Plan reached in the early 1990s helped protect the spotted owl on federal lands.

But, she said, the agency recently agreed that it would complete such a plan — hopefully within 18 months.

Morgan said the Audubon Society chapters would be satisfied if they could get that in writing.

The spotted owl was declared a threatened species primarily because of logging in the old growth forests of the Northwest. That designation led to an 80 percent cutback on logging in national forests and restrictions on private timberlands.

But the number of spotted owls — estimated at 2,400 pairs in Washington, Oregon, Northern California and British Columbia — continues to drop. Logging, wildfires and the barred owl, a natural enemy that has moved in from the Midwest, are all to blame, environmentalists say.

Completing a final recovery plan for the owl would help define what lands are critical to the preservation of the species, Morgan said.

The Audubon Society chapters are asking that the Interior Department and the Fish and Wildlife Service be ordered to commit within six months to a timeline for completing a recovery plan. They also seek legal fees.