The repercussions of the Israeli massacre report are almost certain to affect the future of the government of Prime Minister Menachem Begin and provoke the Israeli public into an even sharper moral debate on their country's role in the Middle East.

The political future of Defense Minister Ariel Sharon and the careers of four senior Israeli Army officers were placed in the most immediate jeopardy by the findings of the commission that investigated last September's massacre of Palestinian refugees in Israeli-occupied West Beirut.

But in the closing section of their 108-page report, the three commission members took direct aim at one of the basic arguments of Begin's allies in the days immediately following the discovery of the Beirut atrocities. It was argued then that because Lebanon has so often been wracked by massacres--some comparable to the Sabra and Shatila refugee camp disaster though they did not seem to shock world opinion--that Israel should feel no particular responsibility to examine its role in the tragic incident. NEWS ANALYSIS

"We cannot justify this approach to the issue of holding an inquiry, and not only for the formal reason that it was not we who decided to hold the inquiry, but rather the Israeli government resolved thereon," the panel declared.

"The main purpose of the inquiry was to bring to light all the important facts relating to the perpetration of the atrocities. It therefore has importance from the perspective of Israel's moral fortitude and its functioning as a democratic state that scrupulously maintains the fundamental principles of the civilized world."

While the Lebanese government of President Amin Gemayel has yet to produce a serious investigation into Lebanese responsibility for the massacre, the Israeli commission's lengthy report was remarkably thorough in examining Israel's role and brutally frank in reporting both the conclusions and the recommendations of the panel.

The inquiry board was appointed last Oct. 1 only after Begin was forced by public pressure to back down from his adamant personal opposition to any investigation.

He contended that suggestions of Israeli responsibility for the massacre were a "blood libel" against the country and the Jewish people.

On Nov. 24, the commission dropped the first shoe, issuing warnings to Begin, Sharon and seven other officials that they were liable to be harmed by its findings. Since then, Israeli domestic politics have been virtually paralyzed while the government and its opponents waited for the outcome of the investigation that came with stunning bluntness today.

When the second shoe dropped today, Begin personally escaped with relatively mild criticism, although he was portrayed as a prime minister who is curiously detached from some of the vital decisions of his government and uncaring about the fates of hundreds of Palestinian refugees who were directly affected by those decisions.

But now the prime minister faces some difficult political decisions, beginning with the place of the burly Sharon in his government.

By his public silence throughout the day, the postponement of any decisions by the Cabinet until at least Wednesday and his reported opposition to firing Sharon or asking him to resign, Begin appeared to be waiting to gauge better the public reaction to the report. He perhaps also was waiting for the pressure on Sharon to build and possibly make any decision by him unnecessary.

For his part, the defense minister gave every sign of digging in for a last-ditch attempt at political survival. His effusive praise of the four Army officers also involved in the investigation, both during today's Cabinet meeting and during a television appearance tonight, indicated he hoped to tie himself to the revered Israeli Army, although he is far from a beloved figure among some of the Army's leadership.

There were reportedly some outright calls for Sharon's ouster in the Cabinet, while other government ministers suggested that he leave the defense ministry post but remain in the Cabinet as a minister without portfolio. But whether such a course would be publicly accepted as conforming to the inquiry board's recommendations was clearly an open question.

Even after Sharon's personal fate is decided one way or another, the Begin government is likely to face weeks of internal turmoil and uncertainty as a result of the report. The prime minister has made no secret of his desire to call early elections this year, believing his Likud Bloc coalition government would be returned to power with a larger majority. But some of the smaller parties in the coalition, whose cooperation would be necessary for new elections, oppose this course.

There was no immediate indication that the leaders of these smaller parties have changed their opinion about early elections. But the picture was far from clear as political figures in all of the country's parties scrambled to judge the impact of the commission report on the future course of Israeli politics.

The main opposition Labor Party issued a statement that, in effect, declared that the report proved what it has long maintained--the Begin government should resign. But Labor Party leaders, as much as Begin, held back on public comments as they appeared to wait for a better reading of the new political landscape.

As for the public, it listened avidly to lengthy excerpts from the report that were read on the radio today, but it was impossible to measure initial public sentiment. The only overt sign of public attitudes indicated the continuing split in the Israeli public that was evident during the war in Lebanon: groups that demanded the immediate implementation of the commission's recommendations and those who opposed the investigation demonstrated simultaneously outside Begin's office today.

There was no comment on the report from the Israeli Army or the four officers directly involved in the probe, including Army Chief of Staff Lt. Gen. Rafael Eitan. But Israel radio reported tonight that senior officers were shocked by the panel's findings, believing them too harsh in dealing with their commanders and damaging to the Army as a whole.

There were also legal questions left unanswered by the commission report. The panel was strictly an investigative unit with no power to bring formal charges.

But the four Army officers--Eitan, Maj. Gen. Yehoshua Saguy, Maj. Gen. Amir Drori and Brig. Gen. Amos Yaron--were all accused of a "breach of duty," a finding that Israeli legal experts said could possibly form the basis for later criminal prosecution.

Beyond the political, legal and moral implications of the report, the findings and their aftermath are bound to have an important impact on Israel's course in the negotiations on a troop withdrawal from Lebanon and a broader Middle East peace settlement.

The impact on these issues was equally impossible to measure initially. However, Begin's office, in an apparent attempt to maintain a business-as-usual stance in the midst of the storm, announced this afternoon that the prime minister will meet with U.S. special envoy Philip C. Habib here Wednesday to discuss the stymied troop withdrawal talks.