Top female chess players reacted with horror yesterday after being told they must compete at next year's world championship wearing a hijab.
Within hours of Iran being announced as the host country, the event was plunged into crisis as it emerged that players taking part face arrest if they do not cover up.
Grandmasters lined up to say they would boycott the 64-player tournament and accused Fide, the game's governing body, of failing to stand up for women's rights. Fide officials, meanwhile, called on participants to respect "cultural differences" and accept the regulations.
Hijabs have been mandatory for women in Iran since the Islamic Revolution of 1979 and the law is enforced by the country's "morality police".
Players claim that Fide is turning a blind eye to sexual discrimination.
Nazi Paikidze, the US women's champion, said: "It is absolutely unacceptable to host one of the most important women's tournaments in a venue where, to this day, women are forced to cover up with a hijab.
Paikidze added: "I am honoured and proud to have qualified to represent the United States in the Women's World Championship. But, if the situation remains unchanged, I will most certainly not participate in this event."
Carla Heredia, an Ecuadorean former Pan American champion, added: "No institution, no government, nor a Women's World Chess Championship should force women to wear or to take out a hijab.
"This violates all what sports means. Sport should be free of discrimination by sex, religion and sexual orientation."
Susan Polgar, the chairman of Fide's commission on women's chess, defended the federation, saying that women should respect "cultural differences".