A U.S. District Court judge yesterday stopped the federal government from accepting bids today on $500 million in offshore oil and gas leases in Alaska's Beaufort Sea because the government had failed to assess adequately the environmental impact of the drilling.

In a 54-page decision, Judge Aubrey E. Robinson Jr. ruled that the Department of the Interior had not fully evaluated the impact of such activity on the welfare of the bowhead whale, an endangered species that migrates through the Beaufort Sea along the north Alaskan coast.

In failing to comply with such requirements under the Endangered Species Act, Robinson said, Interior Secretary Cecil D. Andrus had "shirked his responsibility" to Inupiat Eskimos, natives of the North Slope whose lifestyle depends on hunting and fishing whales and other wildlife.

Robinson said he was compelled to stop the sale, which would have been based on a "substantially flawed" environmental impact statement.

Government lawyers said yesterday that they will take Robinson's decision to the U.S. Court of Appeals. A further hearing on a motion that Robinson postpone enforcement of his decision pending appeal will be held Friday.

Robinson also ruled that the environmental impact statement, filed by the government under the terms of the National Environmental Policy Act, did not meet requirements that a detailed study be completed on any major federal action "significantly affection the quality of the human environment."

Robinson agreed with environmentalists who brought the case that the environmental impact statement did not alert Andrus to "all possible environmental consequences" of the oil and gas lease proposals and had not adequately considered the cumulative effect of the proposal and other projects under way in the North Slope area. Other projects include drilling in the Prudhoe Bay, the Alaska Natural Gas Pipeline and the Trans Alaska Pipeline.

An earlier court decision had noted that to ignore the cumulative polluting effect of such projects "could be so risk ecological disaster," Robinson said in his opinion, released late yesterday.

In the Alaska case the impact statement doesn't discuss cumulative effect on species other than the bowhead whale, such as polar bears and caribou, and discussion on the effect on birds is too vague, Robinson said.

Moreover, Robinson said, there was insufficient evaluation of operating order and lease stipulations in connection with the Beaufort Sea's development, important for minimizing the environmental impact for exploration and drilling.

The environmental impact statement failed to alert the secretary to the probable effectiveness of the stipulations or to various alternatives that could lessen any adverse impact on the environment.

Robinson also said that the government had failed to comply with two sections of the Endangered Species Act. One section requires the Interior secretary to insure that all agency action is not likely to jeopardize the continued existence of an endangered species.The other provides for a "biological opinion" on the likelihood that some species will be endangered by the drilling activity.

Robinson said that a letter written by the National Marine Fisheries Services, which said insufficient information was available to determine the likelihood of endangerment, was "woefully inadequate." The letter did not state what effect immediate activity might have on the endangered species, such as the bowhead.