The identity of the Charedi rabbi who gave his blessing to the controversial petition to the Supreme Court surprised no one.

Rabbi Yaakov Yosef has long made a name for himself in challenging not only the norms of his community, but also the wishes of his father, Rabbi Ovadia Yosef, the most influential Sephardi rabbi of this generation and spiritual leader of the Shas political party.

Much of Rabbi Yosef Jr's contrariness can be traced back to sibling rivalry. Rabbi Ovadya's second child, born in 1946, always found himself competing for his father's affections with favoured eldest daughter Adina, and with his younger brothers and brothers-in-law.

All of the great rabbi's offspring are either rabbis themselves or married to rabbis. For over 20 years, Rabbi Yaakov has served as rabbi of the working-class Bukharim neighbourhood in Jerusalem, but always felt that his brothers received better jobs and were appointed as custodians of his father's legacy.

In 1983, when Shas was founded, he was his father's personal representative in the political arena, first as a member of the Jerusalem City Council and then as a member of Knesset. But he was retired from politics in 1988 after only one term, at his father's orders, since he would not toe the party line.

Since then he has become estranged from Shas, publicly accusing its leaders of corruption and excoriating them for joining the left-wing Rabin government in 1992. He followed up by aligning himself with right-wing rabbis of Lubavitch and the settlers' movement, and become the leader of a small but devoted community, consisting mainly of working class, religious Sephardim, who feel let down by Shas.

For many years, he had no connection with his family. When matriarch of the family, Rabbanit Margalit, died in 1994, he sat shivah separately. Instead, he became very close to his father's arch-rival, Rabbi Mordechai Eliahu, who died this month. In the last elections, he called his followers to vote for the right-wing National Union Party, and not for Shas.

He was the perfect match for the young crusading lawyer, Yoav Lalom, who has sworn to rid the strictly Orthodox school system of its bigoted policies on accepting Sephardi girls. Rabbi Yaakov's own daughter was a victim of the system when she was refused entry to a prestigious seminary.

Rabbi Yaakov encouraged Mr Lalom last year to defy the Charedi taboo against going to the secular courts in his petition against the school in Emanuel. In the face of intense pressure, he has backed him ever since.

But last Friday he announced that he was leaving the campaign after receiving threats. His father said in his weekly sermon that those who go to the secular courts "have no share in the life hereafter" but after a two-day break it transpired that, not surprisingly, he was still involved. When a group of rebel rabbis came to strengthen his spirit, he vowed "to carry on sanctifying God's name".