Len McCluskey has vowed to discipline any member of his UNITE union found to have sent anti-Semitic messages after the man challenging him for the top job was subjected to online abuse from the general secretary’s own backers.

Gerard Coyne is said to be considering calling in the police after being sent messages on Twitter invoking age-old tropes.

One tweet from @1UnionBloke – who has made clear his support for McCluskey – carried an image referring to “Jewish mafia” accompanied with the words: “Be warned @gerard_coyne has backing now!! @UniteforLen.”

Len McCluskey

Len McCluskey

A spokesperson for McCluskey, the hard-left incumbent, told the Jewish News: “Len wants his supporters to support his positive, progressive agenda, which celebrates the inclusive values of our labour movement. He does not want or condone any engagement by them in online abuse.

“Unite has made it clear that any member who has made anti-Semitic comments is in breach of the union’s rules and will face disciplinary action.”

@1UnionBloke sent the post yesterday, writing on the same day: “#proudtobeunion for many years and now supporting @uniteforlen campaign for @unitetheunion general secretary. Saying NO to
Right wing Coyne.”

McCluskey – who remains favourite to win another term next month – has previously suggested Labour’s anti-Semitism crisis was manufactured for “political aims”. He is

The online attacks on rival came within hours of Coyne condemning the “singling out” of the Israeli-Palestinian conflict under the leadership of McCluskey. In an interview with the Jewish Chronicle, he also rounded on the UNITE members on Labour’s NEC who defended two individuals accused of harassment and bullying of Jewish students at Oxford University Labour Club – a move that enabled them the case against them to be thrown out.

Tweet from @1UnionBloke - carried an image referring to "Jewish mafia" accompanied with the words: "Be warned @gerard_coyne has backing now!! @UniteforLen."

Tweet from @1UnionBloke – carried an image referring to “Jewish mafia” accompanied with the words: “Be warned @gerard_coyne has backing now!! @UniteforLen.”