The Interior Department yesterday disclosed details of a secretly negotiated plan to give mineral rights on more than 160,000 acres of potential oil lands in the Arctic National Wildlife Refuge to native corporations in return for surface rights on nearly 900,000 acres of native-held land in other Alaskan refuges.

Congress has not authorized oil drilling in the Arctic refuge, and Interior officials said the proposed exchange would not take place without congressional approval.

But the proposal has added a new layer of controversy to the debate over energy exploration in the refuge, which Interior officials regard as the nation's brightest prospect for a major oil strike and conservationists view as a fragile and irreplaceable wildlife preserve.

The proposed swap was negotiated between Interior and six groups representing 18 Alaskan native corporations, which have agreed to lease the land to major oil companies. The tract selection was completed earlier this month after 18 months of discussion and leaked to The Wall Street Journal.

William P. Horn, assistant secretary for fish and wildlife and parks, said the department had intended to make the proposal public and seek congressional approval, although Interior lawyers believe the department has authority to move ahead on its own.

"We are not engaged in any form of giveaway," Horn said, adding that the plan has been put on hold after several members of Congress sharply criticized it. Earlier this week, Rep. George Miller (D-Calif.), chairman of the House Interior subcommittee on water and power resources, accused the department of "usurping the Congress' authority" and requested an investigation of the plan.

According to Horn, the trade would give the native groups the right to explore for oil on 166,000 acres of the 1.5 million-acre refuge. In return, the corporations would cede surface rights, but not mineral rights, to 891,000 acres in seven other Alaskan refuges, including 260,000 acres of brown bear habitat in the Kodiak refuge and 233,000 acres of prime waterfowl habitat in the Yukon Delta.

Horn said the Interior Department set a $538 million value on the wildlife habitat and the Bureau of Land Management figured the oil tracts were worth the same.

"The lands we've identified represent some of the premier habitat in the state," he said. "We're not talking mountains and ice."

Horn said the proposal would give the native groups about 11 percent of the Arctic refuge's coastal plain, which department officials say has a chance of containing as much oil as the nearby Prudhoe Bay field.

"We anticipate the remaining acreage . . . will generate billions of dollars of revenue, both for the federal Treasury and to be shared with the state of Alaska," Horn said.

However, critics said the trade could cost the government billions of dollars in lost royalties -- should the Arctic refuge prove to be as productive as Interior thinks it is -- and would not protect wildlife habitat in the other seven refuges from mineral exploitation.

"I was frankly surprised that representatives of this administration would consider giving away potentially billions of dollars to private corporations," said Randall Snodgrass of the Wilderness Society.

Conservation groups also accused the department of trying to circumvent environmental laws through the land swap. Once transferred to native corporations, the refuge tracts would not be subject to the rigorous environmental investigations that must precede any federal leasing effort, Snodgrass said.

Horn acknowledged yesterday that the proposed trade would give the native groups a head start of "several years" in exploring the area for oil.

The Arctic refuge was created by the Alaska Lands Act in 1980, but Congress deferred a decision on whether to allow energy exploration there until Interior completed an assessment of its potential oil reserves and wildlife value.

Department recommended last year that the area be opened for drilling. The action touched off a bitter struggle with conservation groups, who contend that the refuge would produce only a few weeks' supply of oil at the risk of damaging lands that are critical to survival of the nation's largest herd of migratory caribou and dozens of other animals.