Labour leader Jeremy Corbyn has been criticised for attending an event organised by Jewdas – a left-wing Jewish group critical of more mainstream Jewish organisations.
It comes after Mr Corbyn promised “watertight” investigations into claims of anti-Semitism within his party.
One Labour MP called his actions “irresponsible and dangerous”.
But a leading Corbyn supporter said his attendance at the event was “not as significant as it’s being made out.”
Jon Lansman, founder of Momentum, told BBC Radio 4’s Today programme: “It was his night off, he had nothing in his official diary, his office didn’t know he was there.”
Mr Lansman said past comments by Jewdas about Israel were “certainly not helpful to Jeremy or the cause of opposing anti-Semitism in the Labour Party”.
But he said Mr Corbyn was keen to meet the leaders of “mainstream Jewish organisations”, adding: “Jeremy is a lifelong anti-racist.”
He said accusations of anti-Semitism in Labour could not be dismissed as “smears” against Mr Corbyn, and there was a widespread problem of “unconscious bias” in the party which needed to addressed by a “programme of education and training”.
A spokesman for the Labour leader confirmed Mr Corbyn had attended the Seder event, a ritual service held on Passover, “with Jewish members of his local community” in a personal capacity and not on behalf of the party.
“He wrote to the Board of Deputies and Jewish Leadership Council last week to ask for an urgent formal meeting to discuss tackling anti-Semitism in the Labour Party and in society,” the spokesman added.
Jewdas, which describes itself as a “radical” and “alternative” Jewish collective, is at odds with mainstream Jewish groups over allegations of anti-Semitism in Labour.
It has accused the Jewish Board of Deputies, Jewish Leadership Council and Jewish Labour Movement of “playing a dangerous game” and previously dismissed anti-Semitism allegations as right-wing smears.
Jonathan Arkush, president of the Board of Deputies of British Jews, said: “If Jeremy Corbyn goes to their event, how can we take his stated commitment to be an ally against anti-Semitism seriously?”
Analysis
By the BBC’s Assistant Political Editor Norman Smith
This was an event just outside Mr Corbyn’s Islington North constituency attended by a number of his Jewish constituents and, it’s said, a senior Rabbi.
But some of the UK’s leading Jewish organisations believe his attendance was, at worst, a provocative snub or, at best, an error of judgement by the Labour leader.
The reason is that his hosts, Jewdas, a radical group of mostly younger left-wing Jews, have been highly critical of allegations of anti-Semitism within the Labour Party.
(They are also strongly opposed to the mainstream Jewish establishment in Britain and threaten to “mercilessly satirize” them).
The Jewish Leadership Council and others have suggested Mr Corbyn has shown a lack of sensitivity and a lack of seriousness about tackling anti-Semitism.
“He still doesn’t get it,” I was told.
So was it a deliberate act of defiance on Mr Corbyn’s part? Or was it an oversight; an act of naivety by a leader attending a constituency event without regard to the possible implications?
Over to you, Mr Corbyn.
The Jewish Labour Movement said Mr Corbyn’s attendance at the Jewdas event “topped off the worst week on record of awful relations between the Labour Party and the Jewish community”.
Spokesman Ivor Caplin, a former MP, said: “When we called on the leader of our party to show moral leadership and take decisive action to stamp out anti-Semitism, this is not what we had in mind.”
In a tweet, Labour MP John Woodcock. a longstanding critic of Mr Corbyn’s leadership, said meeting the group gave the message that “extreme views are OK”. This is deliberately baiting the mainstream Jewish community days after they pleaded with him to tackle antisemitism. And he must know that meeting them now will give his members the message that the group’s extreme views are ok. Irresponsible and dangerous
Labour’s Angela Smith said Mr Corbyn’s attendance was a “blatant dismissal” of the case to tackle anti-Semitism in the party.
The chairman of the Jewish Leadership Council, Jonathan Goldstein, told BBC Radio 4’s Today programme that he had “no issue” with Jewdas and its opinions.
However, he criticised Mr Corbyn for meeting the group “in his first act towards the Jewish community” since his organisation had written to the leader regarding anti-Semitism, because Jewdas had called the letter a “cynical plot”.
The chief executive of the Holocaust Educational Trust, Karen Pollock, said on Twitter it was “mocking and disrespectful”.
But Ian Saville, a member of the Jewish Voice for Labour group, told the BBC he did not see Mr Corbyn’s attendance at the Jewdas dinner as an error in judgement or provocative, adding that it was a “religious event”.
Jewdas responded to the criticism on Twitter, posting: “This has been a difficult week to be a lefty Jew.
“[The Seder] reminded us that the reasons we’re Jewish are the same as our reasons for being revolutionaries: our commitment to making this world better than it is now.”
Labour has been engulfed in a row about attitudes towards the Jewish community after it emerged there was a backlog of some 70 complaints of anti-Semitism within the party that had not been dealt with.
Mr Corbyn has previously apologised for the “hurt” in the failures to address complaints and insisted the party does not tolerate anti-Semitism in any form.
Labour has dropped one council candidate over allegedly sharing posts on social media urging followers to “question the Holocaust”.
The party’s new general secretary Jennie Formby, said in an email to Labour members that the “stain” of anti-Semitic attitudes “must be completely eradicated” within the party.
“We are the party for people of all races and faiths, the party of full equality for all, or we are nothing,” she said.
In an interview with Channel 4 News, Mr Corbyn said the issue would be a top priority for Ms Formby and insisted “absolutely strong and watertight” investigations would take place.