An official at the Iranian foreign ministry claimed that delegates from 30 countries, including Britain, would attend the conference, initiated by President Mahmoud Ahmadinejad.

The president, who claims the Holocaust is a myth used to justify the occupation of Palestinian land, has called for Israel to be wiped off the map and suggested that its citizens could be resettled in Alaska.

Among the first arrivals in Tehran for the two-day forum, called Studying the Holocaust: An International View, was Frederick Töben, who describes himself as an “expert”. Töben, an Australian Holocaust denier, brought his own model of the Auschwitz concentration camp in Poland. He claimed that it proved there would have been no room for the Jews — at least 1.1m — whose deaths there were documented in Nazi records.

Asked why western countries were so outraged, he replied: “The Holocaust equals a lie. Therefore Israel is built on a lie.”

The agenda is chilling. The Iranians have presented the forum in the banal manner of international conferences where experts examine evidence in open debate.

The seminars could have been designed to cause maximum pain to Holocaust survivors and their descendants. Gas Chambers: Denial or Confirmation, is the title of one. Others are entitled Freedom of Speech and the Stance of Holocaust Deniers in the West, and The Current Laws Against Holocaust Deniers.

With no trace of irony, Iranian officials said the conference — sponsored by the Institute for Political and International Studies, a foreign ministry think tank — would include archives, photographs and demographic evidence to establish whether the number of victims was exaggerated.

“Our aim is scientifically to study the Holocaust and listen to both sides before reaching a conclusion,” said Manouchehr Mohammadi, the foreign ministry spokesman for research. “We weren’t involved in this event so we can be a neutral judge. If we conclude that the Holocaust happened, we will admit it, but we are still going to ask why the Palestinians have to pay the price.”

Iranian sources said the conference emerged from a behind-the-scenes struggle. Foreign ministry officials are well aware that it will have a negative impact on the country’s image at a time when Iran is already under pressure at the United Nations over its nuclear programme, support for Hezbollah in Lebanon and Shi’ite groups in Iraq.

Hence, although Ahmadinejad has been publicly flagging the conference for almost a year, foreign ministry officials who were supposed to organise it have been dragging their feet. Forced to go ahead by the president, the foreign ministry tried to portray the conference as an exercise in free speech. It was at pains to point out that Iran has a community of 25,000 Jews. who are protected by the government.

One foreign ministry official said: “Does this conference make sense politically for Iran? No. The conference is being held to answer the questions of the president.” Tony Blair, who was invited, called it “shocking, ridiculous and stupid”.

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