Hope Not Hate described the results as “worrying” and said urgent action needed to be taken against social media accounts disseminating antisemitic ideas.
The charity said: “All too often people on the left have sought to play down antisemitism, ignoring the problem or writing it off as a smear.
“The reality is that a significant number of people on the left have promoted or engaged with antisemitic content.”
Of the 27,000 social media accounts analysed, only “a small number” engaged in “extreme, violent, pro-genocide antisemitism or Holocaust denial.”
Attempts to deny that the left has a problem with antisemitism — which was not in itself considered antisemitic — made up the largest category of Twitter activity flagged as a concern by the analysts.
The report said: “These are people who dismiss the problem as nothing more than smears against the left and or attack those who believe there is a problem.”
Hope Not Hate said in the case of Labour party supporters, denial is often used as a means of defending the leadership of the party.
The most common type of Jew-hate displayed was “conspiratorial antisemitism”, which involves the use of antisemitic tropes.
Of the antisemitic tropes employed, the most common was the suggestion that the “Zionist or Israel lobby” or even “Mossad” was somehow steering UK domestic politics.
“This conspiracy is often also symbolised by individuals such as the Rothschilds who have come to embody the idea of Jewish control for some on the left,” the report said.
The group also found regular references to David Icke, whose name often appeared in statements about Rothschild conspiracies.
“He is one of the most commonly mentioned names among the posts analysed, frequently described as someone who ‘exposes Rothschild Zionism’,” Hope Not Hate found.
According to researchers, one of the reasons that many people on the left reject the idea that their political grouping has a problem with antisemitism is that “they don’t properly understand what is and what is not antisemitic”.
Hope Not Hate’s concerns about conspiratorial antisemitism were supported by a separate poll of 10,383 people, who were asked about a common hate theory.
While half of respondents disagreed with the idea that Jewish people have an unhealthy control over the world’s banking system, a worrying 41 per cent said that they did not know and 13 per cent of people agreed with the statement.
The survey found that men were more likely to believe the conspiracy, with 17 per cent agreeing that Jewish people have an unhealthy control of the world’s banks, compared to just 9 per cent of women.
As well as antisemitic conspiracies, Hope Not Hate said its research into left-wing social media accounts showed antisemitic language was common when discussing issues relating to Israel and Palestine.
When it came to social media accounts which trivialised and denied antisemitism, the report found ‘Israel’ and ‘Palestine’ were “unsurprisingly” two of the most commonly occurring words.
Researchers said that the “singular focus” on criticism of Israel of some on the left could in some instances indicate a problem with antisemitic sentiment.
Of the posts examined, researchers found it was common for left-wing accounts to implicitly or explicitly blame Jews for the policies of the Israeli state.
Left wing criticism of the IHRA definition “showed the extent to which discussions around the Israel/Palestine conflict often end up regurgitating antisemitic tropes”, researchers noted.
“A large number of the posts we examined argue that the IHRA definition, and more specifically the definition’s examples, would curtail freedom of expression, removing the ability of people to criticise the state of Israel.
“There is a line between legitimate criticism of the Israeli state, in line with criticism of any other government, and antisemitism. We’ve found that the strong feelings for the plight of Palestinians in some cases take the arguments over that line.”
The report found that many on the left believe the adoption of IHRA and the fight against antisemitism to be “in conflict with other anti-racist struggles, primarily that of Islamophobia.”
Researchers said it was “increasingly clear” that within some sections of the left there is a lack of understanding about what constitutes antisemitism and what harm it causes.
“More work needs to be done to formulate some guidelines for how the left more generally can support the Palestinian cause without engaging in antisemitism and there needs to be the same intolerance of antisemitism amongst the left that exists towards wider racism and Islamophobia,” the group advised.
As for the Labour Party and Jeremy Corbyn, Hope Not Hate said a lack of action by the party has caused great concern among large sections of the Jewish community.
It said the “quiet readmission” of members formerly suspended for investigation over antisemitism had “led to concerns that the party approach has been to try to make the problem of antisemitism go away rather than to tackle the root causes.”
It also raised concerns over the lack of “tangible repercussions” for Labour MPs such as Chris Williamson, who signed a petition in support of Gilad Atzmon, a musician who has promoted Holocaust deniers.
Hope Not Hate noted that there was also a “real reluctance” from the party leadership to deal with Pete Willsman, a long-time colleague of Mr Corbyn, who accused “Jewish Trump fanatics” of making up allegations of antisemitism in the party.
The group added it was a “disgrace” that Jewish MPs have faced the “worst antisemitic abuse from within the Labour Party”.
Hope Not Hate said the “inability of the Labour Party leadership” to understand or acknowledge the Jewish community’s concern over antisemitism was “particularly chilling when the Labour Party and the left in general hold values of equality and anti-racism as core to their identity”.
