A trade union leader says Labour must change its code of conduct on anti-Semitism, warning the issue is costing Jeremy Corbyn’s party votes.
Unison general secretary Dave Prentis urged the party to adopt all of the examples set out by the International Holocaust Remembrance Alliance.
He said the issue had caused an “unnecessary schism” in Labour.
But he said it was “not too late” – and backed Mr Corbyn to deal with it “once and for all”.
His warning follows similar comments by another major trade union leader, the GMB’s Tim Roache.
Critics say Labour’s code of conduct, which its ruling committee adopted last month, is not as comprehensive as the IHRA version.
Labour does not accept this, saying it has replicated the international definition word-for-word in its code of conduct.
The row centres on a list of “contemporary examples of anti-Semitism” cited by the IHRA, not all of which have been repeated by Labour.
Last week Mr Corbyn said he was confident of resolving the issue through consultation with the Jewish community.
Unison, which is affiliated to Labour, represents public sector workers.
Writing in the New Statesman, Mr Prentis said anti-Semitism “should never have become such a divisive issue, an unnecessary schism in a party that on so many issues is genuinely united”.
Warning it was costing Labour at the ballot box, he added: “But worse than that, it’s harming Labour’s historically close relationship with the Jewish community. And it’s costing us the moral high ground from which to oppose all forms of racial hatred and oppression.”
He added: “Yet it isn’t too late for the party to chart a different course and begin repairing that damage, as Jeremy Corbyn is clearly attempting to do.
“Anti-Semitism in Labour didn’t start under Jeremy, but I am confident that under his leadership it can be dealt with once and for all.”
Mr Prentis said he was “not buying” the claim that following the IHRA version would prevent criticism of Israel.
“If you’re not capable of criticising Israel without being anti-Semitic, then you’re an anti-Semite – and we should make no special exceptions for you,” he added.
On Thursday Mr Roache wrote in HuffPost UK that it was “abundantly clear” that Labour had to “accept IHRA examples of anti-Semitism in full”.
Jewish groups and some Labour MPs have criticised the party over the code of conduct since its adoption.
At the weekend Mr Corbyn acknowledged that most of the Jewish community did not share his backing for Labour’s version, saying this was why the party had reopened a consultation with community groups.