Ultra-Orthodox figures are threatening Rabbi Ovadia Yosef's sons with denunciation, saying they and their father must revoke the halakhic ruling Yosef issued on Friday approving conversions officiated by the military.

Yosef's sons, themselves rabbis and community leaders, yesterday received in the mail a pamphlet entitled "Uprooting everything," containing old halakhic rulings against state conversions and denunciations of Yosef, who serves as spiritual head of the Shas party.

Haaretz has obtained the pamphlet, which ends with a threat to "reveal amazing things in pamphlet number two."

A letter attached to the pamphlet warns the rabbi's sons the writers have quotes from prominent rabbis about Yosef following his last ruling, "which is similar to a Reform ruling...his rulings are null and void."

The writers say they have raised money to distribute 100,000 copies of the pamphlet in ultra-Orthodox communities in Israel and abroad.

They demand the sons "save your father's honor, in his old age he is getting embroiled in an affair which could excommunicate him forever from the world of ultra-Orthodox Judaism. Everyone is still stunned and shocked how the rabbi approved of the Israel Defense Forces officiated conversions - which are Reform conversions for all intents and purposes!"

"Stop while you still can, because the flames will turn into a world war and if you don't retract we shall not rest until your father and his books are denounced and ejected from the Torah world."

The letter also blasts Sephardic Chief Rabbi Shlomo Amar. "How could you let Amar fool your father and degrade him in his old age ... your father's worst enemies didn't do to him what Amar did."

Ashkenazi ultra-Orthodox circles void any conversion that does not require observing traditional Jewish law in the strictest manner.

The pamphlet consists of letters issued over the years by Ashkenazi rabbis, some of them dead, denouncing the state and IDF officiated conversions and blasting any rabbi who recognizes them as "a rebel against our sacred Torah."

The last page is taken from the biography of Rabbi Yaakov Yisrael Kanievsky, known as the Steipler Rabbi, who protested against Yosef's ruling on fallow growing year laws.

The Lithuanian ultra-Orthodox rabbis also attacked Rabbi Yosef yesterday in the ultra-Orthodox daily "Yated Neeman." The Knesset's Constitution Committee is due to debate the IDF conversion bill today, despite Yosef's dramatic ruling.