The Council on Environmental Quality recommended yesterday that the government stop licensing nuclear power plants soon, unless it finds a safe way to store deadly radioactive wastes.

Spent atomic fuel, which is building up rapidly at the nation's nuclear plants, remains radioactive at least 250,000 years. So far, satisfactory permanent storage sites have not been found.

The three member council, which advises the President on environmental issues, also that, before building any nuclear plants, utilities should prove that conservation or solar energy cannot provide the electricity.

The proposal, outlined in a speech by council member Gustave Speth before an American Bar Association conventon here, came as the administration is debating how to shorten the average of 11 years it now takes to licinse and build a nuclear plant. Speth and other nuclear critics have been vying for influence over nuclear policy with Energy Secretary James Schlesinger, who takes a more optimistic view of atomic power.

Changing the rules for licensing plants - as Carter has proposed to Congress - is not enough, Speth suggested yesterday, "Licensing reform . . . is not panacea . . . industry and government energy officials (must) address the underlying and unresoved issue affecting nuclear safety," he said.

"We favor a national decision which would make the expanded use of nuclear power contingent on a clear showing . . . that nuclear power's deadly by products can be safely contained for geologic periods."

Speth proposed a "nuclear deadline" for solving the waste diposal problem. If by the deadline - two years or so, he said in an interview after the speech - no solution has been found, licensing of new nuclear plants should he halted.

Institutional problems may be more severe than the technical problems. Speth suggested in the speech. "The sorry history of radioactive waste management in this country to date provides no basis for confidence that things will work out," he said, citing abandoned wastes at West Valley, N.Y., and unsuccessful attempts to locate a storage site in Kansas.

"Actual field demonstration of the sollution" to the waste problem should be required before new plants are licensed, as before new plants are licenses, as required by a recent California law, Speth said.

Scott Peters, a spokesman for the Atomic INDUSTRIAL Forum, said nuclear wastes can be solidified and buried in stable geologic formations such as salt mines. The Energy Research and Development Administration has begun such a program but "there has been a problem getting on the job," he acknowledge.

Speth denied his speech was a tactical mo in a policy struggle with Schlesinger, but said. "The Administration position on thie issue not firm. We hope to stimulate a robust discussion which will have an impact on the administration."

Licensing reform, Speth warned, should not occur at the expense of citizen participation, as the industry wou have it. COntested plant licenses have taken an average of 29 months, compared to 24 months in uncontestes cases, he added.

Carter's licensing reform bill, which seeks to reduce the time it takes to build a plant, should include an amendment requiring utilities to demonstrate the need for new capacity and the la of a solar or conservation alternative, Speth said.

Although the administration has been accused in Congress of giving short to solar energy in its energy plan and budget, Speth called the sun "our best hope. The time is ripe for a national policy recognizing solar as our highest priority energy supply option and seeking the transformation of our economy to one based increasingly on the sun," he said.

Citing a June report by the Congressional Office of Technology Assessment equipment are already competitive with electricity for heating water and, in some areas residential and commercial buildings . . . Within 10 to 15 years it may be possible to produce electricity from photovoltaic devices that is completitive with new central station power plants."

Increased coal burning, a central element of Carter's energy package, present "grave problem" from strip mining, air pollution and buildup of carbon dioxide gas in the atmosphere, he said.