The conference has drawn criticism from human rights groups.
The two-day conference hosted Western “revisionists” who doubt that the slaughter of six million Jews in World War II took place.
On the second and final day of the conference, Ahmadinejad announced that the conference had decided to set up a “fact-finding commission” to determine whether the Holocaust had happened of not.
He said the commission will “help end a 60-year-old dispute” and called on Western governments “not to harrass members of this commission and [to] allow them to carry out more research and make all issues transparent”.
The head of the new committee, identified as Mohammad Ali Ramin, an Iranian academic, said its members were “not racist or opposed to any particular group”.
“Rather they are just seeking the truth to set humanity truly free,” the ISNA student news agency quoted him as saying.
Criticism of the forum grew as its second day went ahead.
Dana Perino, a White House spokesman, said: “The gathering … in Tehran is an affront to the entire civilised world, as well as to the traditional Iranian values of tolerance and mutual respect.”
“Anti-Semitism has no place in Europe; nor should it in any other part of the world”
Franco Frattini, EU Justice and Home Affairs Commissioner
Tony Blair, the British prime minister, voiced his disapproval of the conference.
He said: “I think it is such a symbol of sectarianism and hatred towards people of another religion – I find it just unbelievable.
“If you’re going to invite the former head of the Ku Klux Klan to a conference in Tehran which disputes the millions of people who died in the Holocaust, then what further evidence do you need to have that this regime is extreme?”
Angela Merkel, the German chancellor, said her country would never accept such a conference and would “counter it in every way we can”.
She said: “It shows the danger of the situation Israel is in and in particular the threat that Israel lives under.”
Franco Frattini, the EU justice and home affairs commissioner, said he wanted to “express publicly my shock and indignation” over the Tehran conference, adding: “Anti-Semitism has no place in Europe; nor should it in any other part of the world.”
The Vatican reacted to news of the conference by describing the Holocaust as an “appalling tragedy to which one cannot remain indifferent”.
A former Ku Klux Klan leader and French professor Robert Faurisson are among those participating in the conference.
Iran said that the aim of the forum was to find answers to questions about the Holocaust.
Ahmadinejad has described the Holocaust as a “myth”, and openly doubts the scale of the slaughter.
The hosting of the conference is the latest controversy regarding Iran. The Islamic republic already faces UN sanctions for failing to agree to halt sensitive nuclear work.
Historians specialising in the Third Reich, basing their figures on original Nazi documents, generally believe around six million Jews were killed in the Holocaust, although some estimates are slightly lower or higher.
Hitler’s government also killed millions of non-Jews.
The European Jewish Congress “condemned in the strongest terms” the “negationist and revisionist” conference in Iran attended by Western figures it described as “pseudo-historians and intellectuals”.