A FURIOUS row about anti-Semitism is being used by Jeremy Corbyn’s opponents within Labour to undermine his leadership, the leader of the UK’s biggest trade union has claimed.

Unite general secretary Len McCluskey attacked a “cynical attempt to manipulate anti-Semitism for political aims”, as the damaging row continued to grip the party in the run-up to Thursday’s election.

The intervention from McCluskey came after controversial comments by ex-mayor Ken Livingstone and MP Naz Shah saw both suspended from the party.

Livingstone, the ex-London mayor, was suspended from the party after saying Adolf Hitler had supported Zionism in the 1930s “before he went mad and ended up killing six million Jews”.

Corbyn insisted that Labour is “united” in opposing anti-Semitism, as he stated that the party “stand absolutely against racism in any form”. “We stand united as a Labour movement recognising our faith diversity, our ethnic diversity, and from that diversity comes up strength,” he declared as he addressed a May Day rally in London yesterday. But the Labour leader faced calls from Israeli politicians and diplomats to give a more “unequivocal” condemnation and warnings – including from the party’s London mayoral candidate Sadiq Khan – that the party would be punished in Thursday’s elections.

Labour is holding an independent inquiry into anti-Semitism and other forms of racism in its ranks – but the leadership’s response to the allegations has been criticised by some Labour MPs.

But ex-minister Ben Bradshaw told the BBC’s Sunday Politics the issue had been allowed to “drag on”. Labour MP Louise Ellman said the response had been “much too slow”. Ellman, who is Jewish, said she had been subject to anti-Semitic abuse herself at a meeting of the local party. A complaint is being investigated.

However, McCluskey, whose union is Labour’s biggest donor, dismissed the controversy as “mood music” being exploited by political enemies of Corbyn.

“Once the mood music of anti-Semitism dies down, then next week and the week after there will be another subject,” he told BBC Radio 5 Live’s Pienaar’s Politics. There was widespread speculation that Labour MPs were coming closer to launching a challenge to Corbyn’s leadership – with a poor showing at the ballot box or a vote in favour of Brexit potentially sparking an internal coup.

However, shadow international development secretary Diane Abbott said it was “a smear to say that the Labour Party has a problem with anti-Semitism”.

Livingstone’s comments linking Hitler with Zionism – for which he has declined to apologise in a string of media interviews – were “extremely offensive”, she told BBC1’s Andrew Marr Show, but not part of any wider pattern. Abbott said: “200,000 people have joined the Labour Party. Are you saying that because there have been 12 reported incidents of hate speech online, that the Labour Party is somehow intrinsically anti-Semitic?”

She said she would be “dismayed if some people were hurling around accusations of anti-Semitism as part of some intra-Labour Party dispute”.

Israel’s new ambassador to Britain said parts of the left were “in denial” about anti-Semitism and criticised Mr Corbyn’s links to groups such as Hezbollah and Hamas.

“There has to be an unequivocal message from leadership saying that there is no solidarity with anti-Semites,” Mark Regev said.