Israeli Prime Minister Shimon Peres and Defense Minister Yitzhak Rabin both strongly criticized President Reagan today for his visit yesterday to the World War II German military cemetery at Bitburg.

Peres called Reagan's decision to lay a wreath at the cemetery during his visit to West Germany "a painful and grievous error." Rabin said Reagan "will not be forgiven either by enlightened humanity or by the Jewish people."

The statements were the strongest yet made by senior officials of the Israeli government, which has taken a deliberately low-key approach to the Bitburg controversy.

The comments by Peres and Rabin, made at separate ceremonies marking the 40th anniversary of the defeat of Nazi Germany, came a day after Ariel Sharon, the minister of industry and trade from the right-wing Likud bloc in the national unity government here, had criticized the Labor Party leaders sharply for what he described as their tepid response to the Bitburg controversy.

"They unfortunately don't know how to stand up to the gentiles," Sharon told a trade union rally last night, according to accounts of those present.

He added that if the Likud bloc's Menachem Begin were still prime minister, "Israel would not have stuttered. He would have spoken to the Americans on this subject clearly and with determination."

Meanwhile, Begin was quoted by The Associated Press as saying in a telephone interview that Reagan's participation in the ceremony at Bitburg, which contains the graves of 49 Nazi Waffen-SS soldiers, was "one of the saddest days in the history of the Jewish people." He made a similar comment in an interview with the Israeli Army radio, United Press International reported.

Peres spoke at the opening meeting of the summer session of Israel's parliament devoted to commemorating the Jewish Holocaust and the defeat of the Nazis.

In celebrating the victory of World War II, Peres said, it was important to ask whether the "lunatic policy" of Nazism had also been eradicated and to remember that in the rise of the Nazis "a part was also played by those who failed to realize its significance, who were inclined to forgive or to ignore."

Referring to Reagan's comment that the German soldiers buried at Bitburg were victims of the Nazis as much as the Jews who died in the Holocaust, Peres said, "Gravestones haven't the power to obliterate the abyss that yawns between those who lead to murder and those who were led."

He added: "I believe that President Reagan is a true friend of the Jewish people and the state of Israel. It is precisely for this reason that we feel deep pain at the painful and grievous error of his visit to Bitburg.

"There can be reconciliation between peoples. There is no reconciliation between times. There is no reconciliation regarding the past."

Rabin spoke at Yad Vashem, the memorial here to the Holocaust victims, at a ceremony to dedicate a monument to the Jewish soldiers, partisans and guerrillas who fought Germany in World War II.

"Today, the day after Bitburg, here at this place of Yad Vashem, let it be said that we, the members of the Jewish people, have taken an oath: to remember and to forget nothing," Rabin said.

"There is no reconciliation with Nazism, the Nazis and everything associated with them," he added. "The historic mistake of President Reagan was in equating murderers with their victims. For this, he will not be forgiven either by enlightened humanity or by the Jewish people."

Despite the strong feelings expressed by officials here today, Israel's ambassador to West Germany, Yitzhak Ben Ari, took part in Reagan's visit yesterday to the site of the Bergen-Belsen death camp. There was a boycott of the ceremonies by other Jewish groups to protest the Bitburg visit.

An official here said today that there had been much discussion of whether Ben Ari should attend the ceremony and that it was finally decided that Israel had made its position on the Bitburg visit clear and that the ambassador, as part of the invited diplomatic corps, would attend "as an act of protocol, but not as recognition of what Reagan did."

To have boycotted, the official said, would have been seen as an insult to the president of the United States, and "Reagan is a friend."

Ben Ari had said yesterday that he went because "it is the right thing to give a sign, and Bergen-Belsen is the right sign. I believe the new Germany can be trusted."

Before today, Peres had said about Bitburg only that "when a friend makes a mistake, he remains a friend, but the mistake remains a mistake."

Aides to Peres said that, with all the criticism Reagan was receiving from others, there was no need for Israel to become deeply involved in the controversy. They also clearly did not want to strain the relationship just before the arrival here of Secretary of State George P. Shultz, who is to attend a Holocaust memorial ceremony Friday.