Israeli Prime Minister Ariel Sharon has urged all French Jews to move to Israel immediately to escape anti-Semitism.
France has seen a spate of attacks against Jewish targets
He told a meeting of the American Jewish Association in Jerusalem that Jews around the world should relocate to Israel as early as possible.
But for those living in France, he added, moving was a "must" because of rising violence against Jews there.
France's foreign ministry said it had asked Israel for an explanation of the "unacceptable comments".
French Jewish leaders, interviewed on France-2 Television, said Mr Sharon's remarks were unhelpful.
"These comments do not bring calm, peace and serenity
that we all need," said Patrick Gaubert, of the International League Against Racism and Anti-Semitism (Licra). "I think Mr Sharon would have done better tonight to have kept quiet."
"It's not up to him to decide for us," said Theo Klein, honorary president of Crif, which represents French Jewish organisations.
France has suffered a wave of anti-Semitic attacks coinciding with renewed fighting in the Middle East.
"We see the spread of the wildest anti-Semitism" in France, Mr Sharon said.
The latest French government figures show 510 anti-Jewish acts or threats in the first six months of 2004 - compared to 593 for all of last year.
In recent years there have been bomb attacks against a number of synagogues and Jewish schools in France.
Jewish tombs have also been desecrated.
Mr Sharon acknowledged that the Paris government had made efforts to tackle the problem.
He added that France faced a new kind of anti-Semitism based on anti-Israeli feelings and propaganda.
He pointed out that France had a large Muslim community estimated at less than 10% of population, or about five million.
Mr Sharon said his advice to French Jews was that moving to Israel was "a must and they have to move immediately".
Correspondents in Paris say this is not the first time that Mr Sharon has spoken about the need for French Jews to leave for Israel, but rarely has he been so blunt.
"We have immediately made contact with Israeli
authorities to ask them for explanations about these
unacceptable statements," said French foreign ministry spokesman Herve Ladsous.
There is reported to be irritation in France at the idea that life for Jews there is becoming dangerous - especially as the government has made every effort to show that anti-Jewish acts will be severely punished.
A week ago President Jacques Chirac rushed to condemn an apparently anti-Semitic attack on a Paris train that turned out to be a hoax.
But his haste only aggravated passions among many in the Muslim community who feel they are the instant scapegoats, observers say.