WARSAW - Leading Holocaust researchers have criticized European Parliament President Jerzy Buzek ahead of his speech at Auschwitz Tuesday, for endorsing the equalization of the Nazi genocide with Communist brutal oppression.

Some scholars call this growing trend "the gravest threat to preserving the memory of the Holocaust," suggesting it serves to exculpate populations complicit in the extermination of their Jewish minorities. "It is inconceivable that the ceremony at Auschwitz will feature an address by a parliament president who entertains initiatives meant to efface and obfuscate the Holocaust," said Shimon Samuels, the Simon Wiesenthal Center's director for international relations. Samuels was referring to a recent speech by Buzek - a former Polish prime minister - in which he lauded members of the European Parliament for "recognizing that the mass deportations, murders and enslavements committed ... by Stalinism and Nazism fall into the category of war crimes and crimes against humanity."

In April, more than 400 members of the European Parliament voted in favor of naming August 23 "European Day of Remembrance for Victims of Stalinism and Nazism," as suggested in the controversial 2008 Prague Declaration, at the end of an international forum on commemoration.

Efraim Zuroff, who heads the Simon Wiesenthal Center's Israel office, said Buzek's statement was part of efforts to "create a historical and intellectual infrastructure to undermine and eventually cancel the current status of the Shoah as a unique case of genocide."

Professor Yehuda Bauer of the Hebrew University called equation attempts "campaigns to marginalize the Holocaust."

Despite the support that equation received in Strasburg, August 23 has not yet been declared as a memorial for both categories of victims. Buzek will speak Tuesday at a ceremony for International Holocaust Remembrance Day at the former Nazi camp of Auschwitz in Poland. Buzek's spokesperson Inga Rosinska said: "The Shoah is unique and the most tragic case of genocide in the history of mankind. There is no comparison. The idea of the European Day of Remembrance for Victims of Stalinism and Nazism (23 August) - is to remember the victims of the communist occupation of Central and Eastern Europe which followed the end of World War II. Those living on the eastern side of the Iron Curtain were unfortunate to wait for their freedom another half century."

According to a number of leading Holocaust scholars, the state-sponsored equation of Nazi crimes with Communist brutality in Eastern Europe is the most serious threat to preserving the memory of the Holocaust. Samuels said the ongoing growth in the power of rightist parties in the European Parliament is fueling the equation campaign.

This phenomenon is especially prevalent in Lithuania, for obvious reasons, says Dr. Laurence Weinbaum of the World Jewish Congress, a historian specializing in Polish-Jewish relations, but in certain circles it is also manifested in Poland. Artur Hofman, spokesperson for one of the main bodies of Polish Jewry, confirmed this, saying this was "the most worrying trend" connected to the prominent role that Jews, acting as individuals, had in Poland's Soviet-controlled Communist regime. Weinbaum agreed with this assertion. "In the Baltic states, especially Lithuania and Latvia, the campaign to consign the victims of the Holocaust and of Communism to the same basket is a transparent attempt to blur Baltic societies' wholesale complicity in the murder of their Jewish populations," he said.

In August, the prime ministers of Estonia, Latvia and Lithuania signed a joint declaration supporting a call to make Aug. 23 a European day of commemoration for victims of both Stalinism and Nazism.

"In Lithuania, equalizing Stalinism and Nazism is a ruse to delete the stain of massive collaboration," Professor Dovid Katz, a Vilnius-based researcher of Yiddish, told Haaretz. "Instead of facing the past, the state deletes the Holocaust as a category and buries it in another paradigm."

The Lithuanian foreign ministry did not reply to a query on this issue.

Weinbaum noted that while "there is a tendency to try and 'contextualize' - as he defines it - the cases in which Poles participated in the annihilation of the Jews in Poland. "Polish society as a whole cannot be seen as a perpetrator-nation, as can be the Lithuanians," he said. While some Poles were complicit in the murder and despoliation of Jews, he noted, "others rescued them."

He said that in Poland, some circles, especially Polish Holocaust scholars, "vociferously oppose" a combined commemoration date. Others support it for nationalistic reasons. "To be sure, no one can or should minimize the untold suffering caused by Communist tyranny, of which Jews were also victims, but common commemoration will only serve to disfigure memory and history," Weinbaum concluded.