In his final days as the U.S. ambassador to Israel, Samuel W. Lewis has reignited the national debate here over former defense minister Ariel Sharon's role in planning the 1982 Israeli invasion of Lebanon and the decision to send the Israeli Army as far north as Beirut.

Lewis, in an interview broadcast last night on Israeli television, corroborated published accounts -- denied today by Sharon -- that in December 1981, six months before the invasion, Sharon outlined his ambitious plans to Philip C. Habib, President Reagan's special envoy in the Middle East.

"Minister Sharon described in some hypothetical detail the concept for what ultimately I guess was called 'Big Pines,' " Lewis said, referring to the code name for Sharon's plan to drive the Palestine Liberation Organization entirely out of Lebanon and install a pro-Israeli, Christian regime in Beirut.

"Habib was, as I was and others of us were, rather dumbfounded by the audacity and the political concept that this seemed to involve," Lewis said. "And Habib reacted at that point very vehemently. . . . He made it extraordinarily clear to Sharon that this was an unthinkable proposition as far as the U.S. government was concerned."

Sharon, now minister of industry and trade in Israel's national unity government, was quoted today as calling Lewis' description of the meeting with Habib "a gross lie." The afternoon newspaper Yedioth Aharonoth quoted the former defense minister as saying:

"It's too bad that in his final, official appearance, the American ambassador didn't feel the need to tell the truth and express remorse over the fact that he, together with Philip Habib and Habib's assistant Morris Draper here, and former assistant secretary of state Nicholas Veliotes in Washington, were the cornerstones of the failure in Lebanon."

Sharon added: "High-ranking figures have already expressed themselves concerning the Americans' failures in Lebanon, of which Ambassador Lewis was the main architect. It's too bad that Lewis didn't understand the damage he caused by his actions and his unreliable reports to Washington. If he had acted with a good deal more responsibility, and had not misled President Reagan in his reports, it's possible that the situation in Lebanon today would be different."

Sharon did not detail his specific complaints against Lewis, but he is known to feel that U.S. pressure kept Israel from doing what Sharon thought it should have in Beirut and Lebanon.

Asked about the dispute Thursday, State Department spokesman Bernard Kalb said that the meeting between Habib and Sharon "was obviously a diplomatic discussion, and as such I have nothing to say about it."

The exchange was the latest example of the deep personal animosity between Lewis and Sharon, which is widely known in Israel. Sharon has always blamed the United States for the failure to achieve his goals in the Lebanon war and named Lewis as the principal culprit. Lewis carefully has refrained from criticizing Sharon in public while working quietly to undermine his political standing in Israel.

Lewis' remarks prompted some left-wing members of parliament to call for Sharon's ouster from the government for betraying "state secrets" to the United States. There were also renewed calls for creation of an official commission of inquiry into the Lebanon war, an idea that has generated little enthusiasm in the past.

When Israel invaded Lebanon on June 6, 1982, the officially announced purpose was to destroy the PLO guerrilla bases in the southern part of the country. Sharon maintained at the time that the spread of the war to include clashes with the Syrian Army and the Israeli drive to Beirut was forced on Israel by military developments on the ground.

Lewis' account of the December 1981 meeting between Sharon and Habib was not new, but it was the first given publicly by a senior U.S. official. A detailed description of the meeting, said to have taken place on Dec. 5, was provided by Zeev Schiff, military editor of the newspaper Haaretz, and Ehud Yaari, Arab affairs correspondent for Israeli television, in their book, "Israel's Lebanon War."

According to Schiff and Yaari, Sharon believed that if he outlined his plans to Habib well before the invasion, "the Americans would grow used to the idea that nothing could stop Israel from mounting a military strike into Lebanon, so they had best reconcile themselves to the idea and prepare to cash in on the benefits."

Lewis, who has been ambassador in Tel Aviv since 1977, will leave on May 31 to become a diplomat-in-residence at the Johns Hopkins University's School of Advanced International Studies.

In the television interview, Lewis said that by early 1982, he and other officials at the U.S. Embassy viewed Israel's intentions toward Lebanon as "a war that was just waiting to happen" and that he repeatedly informed the administration of this.

He said that the possibility of an Israeli drive on Beirut came up only one other time before the invasion, in a May, 1982, meeting in Washington between Sharon and then-secretary of state Alexander M. Haig Jr. Calling Haig's account of the meeting in his book, "Caveat," a "very accurate rendition," Lewis said Haig told Sharon that while no country could dictate to another how it defended its own people, Israel should be certain its actions were "commensurate in the eyes of the international community with the threat" posed to Israel from Lebanon.

"I think everybody went wrong in Lebanon," Lewis said of the war and its aftermath. "All the parties involved made very serious mistakes."

Lewis also repeated his criticism, first made publicly last October, of the timing and tactics surrounding Reagan's Sept. 1, 1982, Middle East peace proposal, which called for negotiations leading to a federation between the Israeli-occupied West Bank and Gaza Strip and Jordan.

"I think the substance of the Reagan proposals are the best balanced and most promising approach toward negotiating peace with Jordan and further expanding the zone of peace in this region," he said. "But I felt at the time that the tactics decided on for presenting the initiative were ill-chosen, and that the timing was wrong and would ultimately prove to be unsuccessful."

Lewis said the United States should have moved to "get the Lebanon mess on the road toward resolution" before introducing a new, overall Middle East peace proposal.