They are two of the world's most outspoken rabbis but this week Rabbi Shmuley Boteach and Rabbi Yitzchak Schochet were at each other's throats in a blazing online row over Jesus, heresy and the race to become Britain's next chief rabbi.
It began after Rabbi Shochet's father, Rabbi Dr Immanuel Schochet, a respected Lubavitch scholar based in Canada, denounced Rabbi Boteach's new book Kosher Jesus as an aid to missionaries, forbidden to Jews to read.
In the book, published next month, Rabbi Boteach, based in the USA, argues that Jews should reclaim Jesus as a Jewish teacher and patriot who observed the Torah and who never claimed to be divine.
Responding to Rabbi Schochet Sr's "bizarre" attack, Rabbi Boteach said in a Huffington Post blog that accusations of heresy were "appalling and libellous".
He added that Rabbi Schochet's father should have disclosed in his openly circulated letter of condemnation that "both his son Yitzchok and I are being openly discussed as possible candidates for the position of chief rabbi of the UK, with significant media speculation as to my candidacy…even though, despite many high-profile endorsements, I have said I am not a declared candidate."
He also took a shot at Rabbi Schochet Jr over an incident 14 years ago when they were publicly debating Rabbi Boteach's book The Jewish Guide to Adultery.
"I will never forget how Rabbi Yitzchok Schochet proceeded to tear pages out of my book in front…of the audience… and cast them on the floor," he wrote.
But Rabbi Schochet, the rabbi of London's Mill Hill United Synagogue, hit back in a blog on the same site, saying that his father had intervened after being "inundated" with inquiries about the book "as the world's leading authority on Christian missionaries".
As for the chief rabbinate, Rabbi Schochet declared: "MP Louise Mensch and spoon-bender Uri Geller are hardly what anyone in the UK would consider high-profile endorsements.
"Furthermore, just as my father doesn't need my input, I've never used him to fight any of my battles."
He added: "Like Shmuley, I've never said that I am a declared candidate either…In several discussions with my father, he told me in no uncertain terms that it is not a position he would want to see me in."
He also rejected the book-tearing claim, explaining that he "did have several torn pages from the book, which I quoted from during the debate, some of which at one point went spiralling to the floor".
Rabbi Boteach said he wrote the book so that Jews could embrace "the truthful version" of Jesus as a Jewish martyr rather than the traditional Christian portrait.
But its main intended readership was Christians, who "today are the state of Israel's best friends" and "hunger to learn more about the Jewishness of Jesus".
Opinions of the merits of the book differ. Rabbi Yechiel Eckstein, of the International Fellowship of Christians and Jews, has praised it as "courageous and thought-provoking".
But Professor Michael Cook, author of Modern Jews Engage the New Testament, said that he found Rabbi Boteach's "comprehension of Gospel development superficial and narrow" and "his polarising assertions clash with the tone of sober Christian-Jewish dialogue".