Israel is marking the 60th anniversary of the liberation of the Nazis' Auschwitz death camp in a low-key way.
Sharon told parliament that Israel could rely only on itself
Israeli President Moshe Katsav is among the world leaders attending the Polish ceremony, but no special commemorations are planned in Israel itself.
In a speech to the Israeli parliament, PM Ariel Sharon said the Holocaust showed the Jewish people could rely on themselves alone for protection.
Israel holds its own Holocaust memorial day each year in the spring.
The BBC's James Reynolds in Jerusalem says it is a quiet day at the city's Yad Vashem Holocaust memorial.
Small groups of visitors are wandering along pathways lined with trees planted in memory of those who gave refuge to Jews during the Holocaust, he reports.
Walter Bacharach, who spent three years in Nazi concentration camps, says: "Every day for a survivor is a day commemorating, remembering, memorising what has happened.
"So in this day we concentrate more on the ceremonial side, but actually, as somebody who survived as I did, every day is a day of memory."
Israel's Holocaust commemoration centres on the Yad Vashem museum
At a forum in Krakow attended by members of the Soviet unit which captured Auschwitz, the Israeli president said the history of the Holocaust should never be distorted.
He called on the European Union to prevent a rebirth of Nazism in young Europeans.
Mr Sharon, in a speech to the parliament, the Knesset, on Wednesday to mark the anniversary, said Israel "has learned the lesson of Auschwitz".
"It has learned to defend itself, to defend its people against its enemies and to serve as a place of shelter for Jews," he said.
"The lesson is that we cannot rely on anyone but ourselves."
Mr Sharon said the Allied countries had known about Germany's efforts to wipe out the Jewish people but had done nothing to prevent it.
And he criticised as anti-Semites those who sought to compare Israel's "legitimate self-defence against the Palestinian terrorists" with the Nazis' treatment of the Jews.
"Sixty years after the liberation of Auschwitz, the evil that begat the horror still exists, and still poses a threat," he said.
"We know we can trust no-one but ourselves."
Israeli Foreign Minister Silvan Shalom attended a special session of the United Nations General Assembly earlier this week which began with a one-minute silence to commemorate the Holocaust.
He said: "For the first time I felt as an equal member of the United Nations."