The statement from the Iranian foreign ministry on Sunday was the latest in a series of remarks from Tehran suggesting that the genocide was exaggerated to boost Israeli interests.
Hamid Reza Asefi, the foreign ministry spokesman, told a news conference: "I believe the crimes committed by the Zionist regime are greater than the Holocaust.
"Unfortunately, the Zionist regime is blackmailing the Europeans with the Holocaust."
Mahmoud Ahmadinejad, the Iranian president, has labelled the Holocaust a myth and has called for Israel to be wiped off the map, comments that drew almost universal international condemnation.
He has called for an academic conference on the Holocaust which he thinks will prove that the number of deaths was exaggerated. Western leaders have criticised the proposal as distasteful.
President Ahmadinejad has
labelled the Holocaust a myth
Iran's press and officials have rounded on the West for what they see as hypocrisy, arguing that satirical cartoons of Prophet Muhammad are allowed but that frank discussion of the historical details of the Holocaust are not.
The United Nations Security Council rebuked Iran for casting doubt on the murder of six million Jews by the Nazis and their allies between 1933 and 1945.