George Galloway says he will sue the head of left-wing grassroots group Momentum for defamation, over allegations of anti-Semitism “smears” in an online row with comedian David Baddiel.

Former MP Galloway said he had instructed his solicitors to take action after he was accused of “anti-Semitism” by Lansman who, like Galloway, is identified with the politics of the far-left.

The two men fell out when Lansman jumped to the defence of Baddiel, who was attacked by Galloway on Twitter as a “vile Israel fanatic,” despite a history of critical comments from Baddiel about the Israeli government.

In a message posted on Sunday, Galloway tweeted: “There will be no supporter of the Palestinian people marching behind vile Israel-fanatic ‘comedian’ David Baddiel.”

Baddiel hit back, writing: “Since I’ve always made it clear that my attitude to that country is entirely meh, I think we can conclude that by ‘Israel fanatic’ George just means Jew. Vile Jew. And that therefore he is an anti-Semite.”

Lansman, the head of Momentum, which was credited with supporting Jeremy Corbyn’s rise to power in the Labour Party, waded into the online fracas “in solidarity” with Baddiel.

In reference to Baddiel, Lansman wrote: “Since he’s a Jew who’s talked about being non-Zionist, there’s no possible reason to call him a ‘vile Israel fanatic’ other than anti-Semitism.”

Lansman added: “There clearly should be no place for @georgegalloway in @UKLabour or in the employment of @talkRADIO.”

In response, Galloway tweeted his innocence, saying he had been maligned as a supporter of Palestinian rights by Lansman and that he had instructed his solicitors to take action against the Momentum chief.

“The use of the defamatory smear of anti-Semitism has gone against supporters of the Palestinian people has, at least for me, gone far enough,” tweeted Galloway.

“I have instructed Solicitors to bring a case for defamation against Jon Lansman, owner of Momentum. I will be calling @jeremycorbyn as a witness.”

He added: “I have never said an anti-Semitic word in my life.”

George Galloway tweets