Prime Minister Menachem Begin was widely reported today to be determined to call for new elections if the commission that is investigating the massacre of Palestinian refugees in West Beirut faults him for negligence of duty.

Begin and eight other officials, including Defense Minister Ariel Sharon, Foreign Minister Yitzhak Shamir and four senior Army commanders, were warned by the judicial board of inquiry yesterday that they may be found guilty of "nonfulfillment of duty" because of various failures before and during the slaughter.

The warnings, contained in a resolution published by the inquiry board and in detailed letters to each of the men, sent a political shudder through the Begin government. At the same time, the procedure of warning the officials and inviting them to submit new evidence is likely to prolong the time before the commission issues a final report and the political debate over its findings begins in earnest.

Each of the nine officials was given 15 days to notify the inquiry board whether he wants to reappear before it, submit new evidence or cross-examine other witnesses. After the 15 days, the possibly time-consuming process of collecting new information is to start. "All bets are off on when the commission will end its work," said Bezalel Gordon, a spokesman for the inquiry board. He said it could be "months" before the inquiry is concluded and it is no longer reasonable to expect a final report by January, as had been speculated.

The inquiry board is an investigative body with no power to bring criminal charges against individuals. Gordon said the fact that only nine of the 42 witnesses who have appeared before the panel received the warnings does not necessarily mean that any adverse findings will be confined to them. He said the inquiry board can notify others and can later notify any of the nine that they were no longer in jeopardy.

All of the officials are expected to respond to the invitation to present new information, although some, including Begin, may not ask to reappear before the panel.

With the top echelon of the government and military now on notice that it may be charged with negligence in connection with the massacre, the inquiry board -- however long it takes to complete its task -- sits like a time bomb in the midst of the Israeli body politic. Speculation has already begun here that findings such as those suggested by the commission's resolution would force Begin to defend himself and his government by calling for new elections.

Today, two of the country's most influential independent newspapers, Haaretz and the English-language Jerusalem Post, quoted a source close to Begin as saying that was his intention "if even the slightest blame or shadow of criticism" is directed at him.

The Jerusalem Post said that Begin is "confident of being returned to power with a much larger majority than at present."

The warnings to such key figures in Israel's civilian and military leadership clearly pose the gravest threat to the Begin government since its reelection in 1981. However, as long as the investgation is continuing, the political opposition to the government is likely to be muted on this issue.

At a special briefing for foreign correspondents here today, Gordon stressed that the warnings were not an "indictment" and that "no one is being accused." However, it seemed unlikely that the politically sensitive panel--composed of the chief justice of the Israeli Supreme Court, another justice and a reserve Army general -- would publicly serve notice on the prime minister and other senior officials without at least having reached tentative conclusions about the evidence.

Begin strongly opposed creation of the inquiry board, charging that any suggestion of Israeli responsibility for the massacre was a "blood libel" against the country and its people. But under intense domestic and international pressure, the Israeli Cabinet agreed to establish the panel and did not limit the scope of the investigation.

Almost from the beginning, the inquiry board made clear that it would not confine itself to the responsibility of Army commanders who were near the Sabra and Shatila refugee camps during the massacre, but would also examine the decisions and conduct of the civilian government leadership. No witnesses suggested there was a direct Israeli role in the massacre, which is attributed to Lebanese Christian militia forces.

All nine officials were warned they may be found guilty of "nonfulfillment of duty." Two of them, Lt. Gen. Rafael Eitan, the Army's chief of staff, and Brig. Gen. Amos Yaron, commander of Israeli forces in the Beirut area, were told they may be faulted for "breach of duty." According to Gordon, this is a more serious potential charge that could serve as the grounds for subsequent criminal prosecution.

Issuance of the warnings to the nine officials signaled the end of the first phase of the investigation by the inquiry board itself, which is not scheduled to hear more witnesses. Since the inception of the investigation in October, the panel has questioned witnesses from the prime minister to Army enlisted men. Gordon said staff investigators for the inquiry board will continue their work, including interviewing witnesses.

The warnings to the nine officials were issued under a provision of Israeli law requiring such notification if it appears that "a particular person is liable to be harmed by the inquiry or by its results." Gordon said the definition of "harm" is broad, including damage to reputation, and is not confined to findings of criminal conduct.

The warnings, Gordon added, dealt only with conduct surrounding the Beirut massacre and not possible cases of perjury before the inquiry board. A number of the witnesses who testified in public contradicted one another and one of the nine officials who has been warned, Avi Dudai, Sharon's personal assistant, was accused by another witness of lying.

Gordon said prosecution of any alleged cases of perjury will be left to the Israeli attorney general.