After its publication, doubts were raised about the letter and there were claims the signatories were misled as to its content before they signed. Mr Stern and Mr Friedman denied this, insisting that some of the rabbis even made their own amendments.
Three of the signatories, Rabbis Eliyakim Schlesinger, Azriel Schechter and Ze'ev Feldman, all confirmed they had read and signed the letter.
The letter was written in response to the accusation by the former Chief Rabbi, Rabbi Lord Jonathan Sacks, that Mr Corbyn’s remarks about British Zionists not understanding "British irony" were “the most offensive statement made by a senior British politician” since Enoch Powell’s infamous Rivers of Blood speech.
Mr Stern and Mr Friedman also took issue with the results of a JC poll which found four in ten British Jews surveyed would consider making aliyah if Mr Corbyn became Prime Minister.
The pair told the JC they believe the Labour Party’s antisemitism crisis is a “smear with a Zionist agenda”, describing it as “cruel and unjustified”.
They also accused the Board of Deputies and Jewish Leadership Council (JLC), the mainstream communal bodies that have been critical of Mr Corbyn, of “chutzpah”, saying they “only represent a very particular part of Jews who are pro-Israel”.
The letter, first published on September 7, read: “We were shocked to learn about those that are claiming in the media that the Jews of Britain are outraged towards the Labour Party’s respected leader, Jeremy Corbyn.
“They have spread rumours that the Jewish population are considering leaving the country for fear he becomes Prime Minister.
“We therefore feel necessary to clarify that we have no connection whatsoever with these irresponsible remarks.
“Jews are faithful to G-d and his Torah, and seek the peace of the country they reside in and respect their leaders and, heaven forbid, will not attack their political leaders.”
A JCC spokesman said: “After making our enquiries by the lead rabbis behind the letter, we can hereby confirm the letter is authentic and is genuinely signed by the leading rabbonim of our community in full faith.”
Rabbi Avrohom Pinter, a leading Charedi rabbi, told the JC the letter was genuine, but suggested some of the signatories were unhappy with its criticism of mainstream Jewish representative bodies.
Although he did not sign the letter himself, the rabbi said the signatories' main motive was a desire to “stay out of the argument with the Labour Party”, as well as a feeling that Rabbi Lord Sacks “went over the top”.
Rabbi Pinter said: “There are some people who believe the Jewish community should keep a low profile. The feeling is that we’re in for a good hiding, whatever happens.
“If Jeremy Corbyn becomes Prime Minister we’re in trouble. And because a lot of people have put their hopes in him – a lot of people who have nothing – we will get blamed if he doesn’t win an election.
“I heard some were unhappy with the letter – and if it is true, I think it is that some didn’t want to use the letter to attack the Board of Deputies or the JLC, in the way it has been portrayed.”
Mr Stern, 33, and Mr Friedman, 48, told the JC they have acquired a five signatures since the letter was published, taking the total to 34.
Mr Friedman is a member of the prominent Padwa family. Rabbi Ephrayim Padwa was among the signatories.
