"Its main aim is to create an opportunity for thinkers who cannot express their views freely in Europe about the Holocaust."
The event, which Iran has said will question whether gas chambers were actually used against the Jews, has drawn criticism from Holocaust survivors, Jewish organisations, human rights groups and Western governments.
Sessions at the two-day conference, held at the foreign ministry's Institute for Political and International Studies, were to include Holocaust: Aftermath and Exploitation and Demography: Denial or Confirmation?
The conference was inspired by Mahmoud Ahmadinejad, the Iranian president, who since coming to power last year, has been criticised for comments referring to the Holocaust as a "myth" and calling Israel a "tumour".
Among the participants was American David Duke, a former Louisiana Republican representative. He praised Iran for hosting the event.
"There must be freedom of speech, it is scandalous that the Holocaust cannot be discussed freely," said Duke, a former Ku Klux Klan leader. "It makes people turn a blind eye to Israel's crimes against the Palestinian people."
French writer Georges Thiel, who has been convicted in France for spreading revisionist theories about the mass extermination of Jews, said the Holocaust was "an enormous lie".
"Jewish people have been persecuted, that is true, they have been deported, that is true, but there was no machinery of murder in any camp, no gas chambers," he said.
Jewish rabbis attended the conference
alongside European and American academics
Participants included about half a dozen Jews from Europe and the US, some wearing badges depicting the Israeli flag crossed out. One wore a badge saying: "A Jew, not a Zionist."
"We came here to put the Orthodox Jewish viewpoint," said British Rabbi Ahron Cohen. "We certainly say there was a Holocaust... But in no way can it be used as a justification for perpetrating unjust acts against the Palestinians."
The conference has upset Iran's 25,000-strong Jewish community, said Moris Motamed, the sole Jewish representative in Iran's parliament.
"Denying it [the Holocaust] is a huge insult," he said. "By holding this conference, they [the government] are continuing to insult the Jewish community."
Many ordinary Iranians admitted to embarrassment about the event, which follows Iran's decision to hold a competition for cartoons about the Holocaust in October.
A former senior government official, who declined to be named, said that hosting the conference was unwise given diplomatic pressure on Iran over its nuclear programme.
He said: "Such conferences should not be held."