A Wyoming prospector who stakes uranium mine claims for major oil companies told Congress yesterday some of them do nothing to develop the valuable energy resources they hold on public lands.

"The large, known uranium deposits and the attractive potential uranium bearing acreage in Wyoming and other Western states are eighter owned or controlled by a few major companies - primarily major oil companies," John W. MacGuire told the Senate antitrust and Monopoly Subcommittee yesterday.

"The present mode of operation of many . . . it to acquire and hold as much public land as possible without regard to the diligent development of the property," he complained. "In effect, they tie up vast amounts of uranium acreage and have been unwilling to allocate the financial resources necessary for full and timely development of such acreage."

Holding the resources without development them has had a "decided effect" on uranium prices in the United States, he said. "Prices today are six times what they were three years ago: certainly this is inducement to grab and withhold from competition as much acreage as possible by whatever means available."

The subcommittee is holding hearings on a bull sponsored by its chairman, Sen. Edward M. Kennedy (D-Mass.), and 10 theres to bar major oil companies from owning or controlling any coal or uranium resources.

MacGuire told the hearing that the "power of manipulation' of the major oil companies within the uranium industry must be curbed to allow competition. With their ownership of alternative sources of energy, they have no incentive to develop fully the energy sources that are cheaper to produce - uranium and coal - until they reach a market price equivalent in terms of British Thermal Units to oil and gas, he said.

"If the same parties are selling both, I question it . . . because you'll sell the property that produces the most profit," he said. "You'll develop - put the money - into the one that will produce the most profit.

MacGuire said his firm, Nationa Service, Inc., is the largest claim staking service operation in the United States Oil companies and others essentially contract his services to stake claims for them.

Under the Mining Law of 1872, the companies staking claims on public lands are required to spend $100 a year in exploration to maintain each claim of 20 acres; Questioned by Kennedy, MacGuire said he believed there were problems and irregularities in the compliance of the law the Interior Department administers, and he is currently litigating the validity of the claims of two companies. He specifically praised Exxon Corp. for being "the exception. They are not acquiring more than they are developing," he said.

In other testimony:

William E. Slick, Jr., senior vice president of Exxon Co., U.S.A., denounced the pending legislation, saying it is anticompetitive to foreclose entry into new energy industries to any group of companies, including oil firms. He defended Exxon's record of performance in both coal and uranium production, noting that both recently initiated programs had grown significantly since they entered.

William F. Haddad, director of the New York State Office of Legislative Oversight and Analysis, agrued that the international energy companies have become "an invisible government, above law" with the ability to affect citizens' lives dramatically.

Shearon Harris, chairman and chief executive officer of Carolina Power and Light Co. opposed mandatory divestituve by energy companies of all but one energy source but said he would support a measure with a triggering device so that a company found to be acting in an anticompetitive manner would automatically have to spinoff the affected resource.