A network of Jewish Labour members has backed Jeremy Corbyn over claims the party has become "institutionally anti-Semitic" under his leadership.
Some 200 Labour supporters signed a Jewish Voice for Labour letter calling Mr Corbyn's party a "crucial ally in the fight against bigotry".
Anti-Semitism on the left is "abhorrent but relatively rare", it argues.
The Board of Deputies of British Jews said the view ran "counter to the experiences of Jewish Labour members".
On Wednesday, Labour front-bench MP Barry Gardiner made an emotional apology to Jewish people "let down" by the party.
"We will not stop working until we have once again become a safe and welcoming political home for people from the Jewish community as from every other," Labour's international trade spokesman told the Commons.
Liverpool Wavertree MP Luciana Berger quit the party for the new Independent Group on Monday, saying she had been subjected to "thousands of messages of anti-Semitic abuse and hate".
Telling MPs she had been met with "obfuscation, smears, inaction and denial" after raising the problem, Ms Berger said she arrived at the "sickening conclusion" that the Labour Party was "institutionally anti-Semitic".
But the letter drafted by Jewish Voice for Labour, which describes itself as offering "a space to explore and debate the many questions that are important to us as progressive Labour Jews", rejects the suggestion.
'Formidable' record on campaigning
"The Labour Party under the progressive leadership of Jeremy Corbyn is a crucial ally in the fight against bigotry and reaction," says the letter, published in the Guardian.
"His lifetime record of campaigning for equality and human rights, including consistent support for initiatives against anti-Semitism, is formidable. His involvement strengthens this struggle."
The group says the letter was signed by filmmaker Mike Leigh, writer Michael Rosen and author Gillian Slovo, as well as several academics and Walter Wolfgang, 93, who fled Nazi Germany as a child.
It backs the Labour Party's endorsement of freedom of expression on Israel and on the rights of Palestinians.
However, Board of Deputies President Marie van der Zyl said: "The usual bunch of anti-Semitism deniers have written to the Guardian to declare that anti-Jewish hate in the Labour Party is rare."
She said the letter was "particularly disrespectful" to Ms Berger who had suffered "years of anti-Semitic abuse, much of it from fellow party members".
"This crisis will only be ended once the denial stops and Labour takes this problem seriously. Our community cannot have any confidence in Labour until the leadership commits to action."
Jewish Voice for Labour was formed in 2017 and has consistently backed Mr Corbyn's leadership.
It is separate to the Jewish Labour Movement, formed in 1903, which has called extraordinary general meetings for 6 March, reportedly to discuss ending its 99-year affiliation with the Labour Party.