PARIS, SEPT. 15 -- A wave of indignation swept across France today over remarks by a rightist presidential candidate, Jean-Marie Le Pen, suggesting that the existence of Nazi gas chambers is only a "detail" in World War II history.

The furor appeared to be a significant setback for the hopes of Le Pen and his extreme-right National Front to make an impact on French politics with their presidential campaign.

The candidate, known for controversial comments in the past, had been making a noticeable effort recently to moderate his tone and broaden his appeal for next spring's elections. A number of French political and other figures said, however, that the remarks about World War II gas chambers have exposed Le Pen's far-right beliefs and made him unworthy of further consideration.

Opinion polls have given Le Pen only about 10 percent of the prospective vote. But his candidacy, focused heavily on resentment against North African immigrants, already has played an important role in forcing other potential candidates to address the issue of racism and the fate of immigrant workers.

"Today Mr. Le Pen has thrown down his mask in adopting the theses of revisionist pseudo-historians who deny the existence of gas chambers and the scope of the genocide or who try to make it banal," said a statement from the Representative Council of French Jewish Institutions, the country's main Jewish group.

Jacques Toubon, secretary general of Prime Minister Jacques Chirac's Rally for the Republic, said he was "aghast" at Le Pen's comments.

"This declaration is scandalous and dismaying but I am sure that no Frenchman has forgotten history," Toubon added.

Jack Lang, a Socialist Party leader and former culture minister, called on Toubon and Chirac's other followers who have said they deplore Le Pen's comments to "put their actions into harmony with their words."

"One hopes in particular that they will not fail to insist that the head of the government, Mr. Chirac, break agreements with this neo-Nazi party reached in numerous French regions by the Rally for the Republic and the Union of French Democracy," its coalition partner, he said. "One would not understand that the rare anti-Le Pen ministers could continue to be part of a team whose captain endorses and sponsors a multitude of local pacts with the National Front."

Local officials of Chirac's party have worked out electoral agreements with the National Front for some recent city hall and regional elections. On the national level, however, Chirac repeatedly has said he will not deal with Le Pen in an effort to broaden his appeal to the right next spring.

In what appeared to be an appeal to halt even the local arrangements, Chirac's secretary of state for human rights, Claude Malhuret, said Le Pen's remarks are "an excellent lesson for those who try to persuade us that democrats can accept compromises with extreme right theses without betraying themselves."

As the condemnations poured in, Le Pen's office issued a statement saying he had not intended to deny the existence of Nazi gas camps. Le Pen declined further comment but his aides said he will respond Wednesday.

Le Pen's remarks were made in a radio interview Sunday night in which he was asked his opinion about revisionist historians who seek to show that the extermination of Jews did not take place as commonly described in history books. After declaring his support for freedom of thought, he said: "I have a certain number of questions. I do not say that the gas chambers did not exist. I was not able to see any for myself. I have not specially studied the question. But I think it is a point of detail in the history of the Second World War."

When the radio reporter suggested the gas chambers question was more than a detail, Le Pen responded: "Yes, it is a point of detail in the war. Do you want to tell me that it is revealed truth that everybody must believe? That it is a moral obligation? I say there are historians who debate these questions."