Israel's direct military intervention against the Syrian Army in central Lebanon this week has posed a potential political liability for Prime Minister Menachem Begin that could become the first major foreign policy issue of the current general election campaign.

The opposition Labor Party, which at first seemed somnolent when questions about Begin's handling of crisis management were raised in the early stages of the Lebanese fighting last month, has begun to stir with anticipation of the first real fight of the campaign for the June 30 election. a

The growing perception in the party is that Begin misread the Reagan administration's attitude toward possible Israeli military action in central Lebanon, while at the same time failing to send clear enough warning signals to Syrian President Hafez Assad until it was too late.

The result, according to a growing consensus among Labor officials, was an escalation of tactical feints by both Syria and Israel -- the shooting down of two Syrian helicopters by Israeli warplanes Tuesday in the first such publicly announced attack against the Syrians in direct support of the Christian militias in central Lebanon, the subsequent Syrian deployment of SA6 surface-to-air missiles in eastern Lebanon and renewed threats by Israel that it will not tolerate the continued bombardment of the Christian forces in spite of the presence of the missiles.

Begin has not yet responded publicly to the challenges to his performance, except to maintain that Tuesday's military action was needed to prevent the "annihilation" of the Christians and to prevent the Syrians from moving farther south toward the Israeli border.

With increasingly stern admonitions from the United States aimed at restraining Israel -- further belying Begin's now diminishing perception that there was a basic change in the Reagan administration's attitude toward military action in Lebanon -- the prime minister has been portrayed by his opposition as overplaying his hand in the wrong place at the wrong time.

The contention about Begin's crisis-management performance began to surface tentatively yesterday in a closed-door meeting of the Foreign Affairs and Defense Committee of Israel's parliament.

As frequently happens in Israeli politics, the main thrust of the Labor Party's criticism was deflected by a peripheral issue, and committee members fell into bickering over allegations that young toughs hired by Begin's Likud Party had hurled tomatoes and oranges at Labor Party leader Shimon Peres as he attempted to speak at a traditional picnic celebration of Moroccans on Sunday.

Peres fired the opening salvo on the Syrian question by asking the committee how Begin could announce on television Israel's first direct military intervention on behalf of the central Lebanses Christians without at least advising the opposition parliament faction.

Begin replied that he had intended to do that and at the same time express regrets to Peres about the fruit throwing, but that when he heard that the Labor Party had blamed the Likud for the picnic disruption, he decided to punish its "impertinence," according to committee sources. The meeting then reportedly erupted in a shouting match and was abruptly adjourned.

But afterward, the Labor Party's nominee for defense minister, former Army chief of staff Haim Bar-Lev, told reporters that he does not see any reason for Israel going to war with Syria. But, he said, the Syrians should have been given a better understanding in the beginning of their offensive of where Israel stands in support of the Christians.

It was Bar-Lev who two weeks ago publicly demanded a parliament committee debate on the Syrian problem, but his Labor Party colleagues brushed the proposal aside, apparently not realizing that his intention was to focus criticism on Begin's performance in crisis management, party sources said. Begin, besides being premier, is also defense minister.

Early in the week, before the downing of the helicopters and the deployment of the missiles, Labor members of the parliament appeared to adopt a hard-line position on the Syrian shelling of Christian positions. The only criticism directed at Begin then appeared to be that the prime minister had been too hesitant in warning the Syrians.

Following this week's developments, opposition leaders have shifted their focus on Begin, saying that the downing of the helicopters -- and consequently the deployment of the missiles -- could have been avoided had Begin been less ambiguous in his signals to Damascus.

Party spokesmen have pointed out that at various times, Begin's public alarms concentrated on any Syrian presence in Lebanon, the intensity of the shelling of Zahle, the attempt to dislodge the Christians from Sanine Mountain and the alleged use of assault helicopters against the Christians. The only possible result of such diverse warnings, the opposition leaders say, could be Syrian confusion about what Israel was saying it would not tolerate and a conclusion by Assad that the Israeli warnings were more rhetorical than ominous.

Now, according to the Labor Party interpretation, the Syrian missiles are in place and Israel is under intense U.S. pressure not to make any moves in central Lebanon, while there is no guarantee that the Syrians will not use the threat of their poised commando units to force the Christian forces into a cease-fire agreement stipulating future ties between the Christians and the Syrians and a severing of Christian contacts with Israel.