Senate Minority Leader Robert C. Byrd (D-W.Va.) yesterday deplored what he described as a steady stream of leaks and loose talk from the Reagan administration in the week before the April 14 military strike against Libya.

A study by the Senate Democratic Policy Committee shows the leaks amounted to a "hemorrhaging of vital military information and planning" that could have jeopardized the mission, said Byrd, the group's chairman.

"The military action was undertaken only after a full week of news reports that quoted administration officials revealing the nature of the mission, against whom the raid would take place, roughly when it would occur, what targets would probably be struck, and which countries would and would not assist it," he said in a Senate speech.

One report on newsstands before the Libyan raid, in Time magazine's edition dated April 21, quoted a top intelligence official as saying leaks were so damaging to U.S. planned action that the raid had to be postponed at least once, Byrd said.

CIA Director William J. Casey has recently talked of possible criminal prosecution of five news organizations for publishing details of U.S. intelligence-gathering operations, particularly reports about intercepted Libyan messages. The Democratic Policy Committee study did not address that issue.

The committee's study -- "The Not-So-Secret Raid Against Libya" -- gives a day-by-day chronology of events and news reports following the April 5 bomb explosion in a West Berlin discotheque that killed a U.S. soldier and a Turkish woman and injured 204 people.

On April 7, U.S. Ambassador to West Germany Richard R. Burt said on NBC's "Today" show that "there are very clear indications that there was Libyan involvement" and that President Reagan was studying the question of military action "right now."

That evening, ABC's "World News Tonight" quoted U.S. intelligence sources as saying that "after the bombing, there were messages from Libya to its embassy in East Berlin which indicated clear knowledge of details of the terrorist attack and which in essence offered praise for a job well done." CBS's "Evening News" cited "intercepted messages dispatched from Libya to its operatives in East Berlin."

The next morning, April 8, The Washington Post reported that Burt had been told to be "more circumspect in his public statements" but said U.S. officials had confirmed the accuracy of his remarks. The Wall Street Journal, meanwhile, reported that Reagan was studying several possible measures, such as a strike against two Libyan missile sites. That night, CBS' "Evening News" reported that the administration had "reached a consensus for military retaliation" and discussed possible targets.

The New York Times reported April 9 that a State Department official who had been openly skeptical of evidence used to link Libya to last December's Rome and Vienna airport attacks was now saying "I have absolutely no doubt this time. We have the goods." ABC's "World News Tonight" said a strike against Libya was in the works.

On April 10, USA Today reported two U.S. aircraft carrier battle groups were ordered to remain in the Mediterranean, and NBC's "Nightly News" said the Defense Department was making "final plans for a retaliatory strike."