Switzerland has joined other European counties in condemning a conference held in Iran which has questioned the Holocaust.
A Swiss foreign ministry spokesman said that it was "unacceptable" to doubt the Holocaust's existence.
Iran called the two-day meeting, which finished on Tuesday, because it said it wanted to debate what it calls taboos surrounding the Holocaust. Participants at the event in the capital Tehran included white supremacists and Holocaust deniers.
Around six million Jews are estimated to have been killed by the Nazi regime during the Second World War.
Swiss Foreign Ministry spokesman Johann Aeschlimann said on Tuesday that the ministry condemned any querying of the right of Israel to exist, as had once again happened in Tehran, and of the Holocaust.
"The Shoah is a historical fact. It is unacceptable to call this into question," he said.
According to reports, Iranian President Mahmoud Ahmadinejad used the end of the conference to say that Israel would one day be "wiped out" just like the Soviet Union.
International reaction to the Tehran conference has been strong, especially in Europe where it is a crime in countries such as France and Germany to deny the Holocaust.
The European Union called it an "unacceptable affront" to the victims and British Prime Minister Tony Blair called it "shocking beyond belief".
German Chancellor Angela Merkel said her country repudiated it "with all our strength." She stood alongside visiting Israeli Prime Minister Ehud Olmert, who denounced the meeting as "unacceptable" and a "danger" to the western world.
The White House has also condemned the conference, as have Jewish groups in many countries.
Switzerland has in the past condemned controversial comments on Israel made by Ahmadinejad.
Last December the hard-line Iranian president caused international uproar when he claimed the Holocaust was a myth.
Switzerland adopted anti-racism legislation in 1994, among other things to prevent revisionist views about the Holocaust.
But the country has sometimes come in for criticism over its neutral stance during the war and its refugee policies during that time.
In its final report in 2002 an independent panel concluded that Switzerland's wartime governments had sometimes failed to meet their humanitarian responsibilities.
swissinfo with agencies
The two-day conference in Iran provoked widespread international outrage.
Switzerland joined in this condemnation on Tuesday, calling denying of the Holocaust unacceptable.
It said it would not tolerate any calling into question of the right of Israel to exist.