Jeremy Corbyn’s biggest union backer has accused the Jewish community of “intransigent hostility” towards Labour and claimed the party’s anti-Semitism problem has been “wildly exaggerated”.

Unite boss Len McCluskey said the issue risked turning the party into a “vortex of McCarthyism” and blamed Jewish leaders for their “utter refusal” to accept an olive branch from Mr Corbyn.

The Board of Deputies of British Jews - which Mr McCluskey singled out for criticism - said he was guilty of an “unfair and unwarranted attack” on the Jewish community.

It came as a YouGov poll found that less than half of Labour voters think Mr Corbyn is doing a good job.

Mr McCluskey’s intervention at such a highly-charged time piles yet more pressure on Mr Corbyn, who has faced a week of questions over his attendance at a ceremony to honour the terrorists behind the 1972 Munich Olympics massacre of Israeli athletes.

Writing for The Huffington Post, Mr McCluskey, whose union is Labour’s biggest financial backer, claimed that he was “at a loss to understand the motives” of Jewish leaders, adding that they had “simply refused to take ‘yes’ for an answer”.