A massive federal sale of West Coast offshore oil leases was denounced here today by a panel of local environmentalists, who charged the federal government has failed to conduct an adequate study of the potential impact of petroleum exploration proposed for the northern California coast.

The U.S. House Select Committee on the Outer Continental Shelf heard testimony from conservation group officials opposed to the opening of 1.3 million acres of ocean bottom off the California coast for exploration by private companies. The environmentalists claimed any oil drilling would pose a serious threat to the local tourist industry, coastal marine habitats, and the region's $26 million-a-year fishing industry.

"The tracts included in the [proposed] lease sale read like a Who's Who of the most treasured and sensitive parts of the coastline," said Richard A. Charter, chairman of the Friends of the Coast, an organization based in Point Reyes Station. "A lease in this region should not even be considered until adequate [environmental] studies are complete."

The dispute involves 240 separate offshore tracts on the outer continental shelf that extend from the city of Santa Barbara in southern California to the state's northern border. The federal government is currently evaluating the environmental impact of the proposed sale. The tracts lie atop an estimated 500 million barrels of oil.

Environmentalists testifying today said the government has largely ignored their objections to the scheme, and had failed to take into account its impact on the area's unique population of sea lions, birds and fish that includes several endangered species. They attacked government efforts to expedite the lease sales, and asked that they be delayed for several years until their ecological effect could be fully weighed.

The calls for delay were angrily opposed by several oil company officials who testified earlier that the environmental issues had already been adequately explored.

"Industry has been making and will continue to make every effort to comply with the complex and stringent requirements" placed on offshore drilling activity, said J. H. Silcox, a spokesman for the Western Oil and Gas Association. "These delays . . . have cost the nation untol billions of dollars and have been a major contributor to our virtual energy enslavement by OPEC."

The House select committee is scheduled to continue hearings on the issue next month in Washington.