The JC was also contacted by an angry Jewish resident who lived in one of the flats above the hotel who said they had lodged their own complaint with Holiday Inn management.
In a statement the hotel confirmed they too had decided to cancel the event.
Mr Williamson claimed on Twitter that the Holiday Inn “had to cancel after two men turned up to threaten their staff.”
He added: “They also had abuse on personal social media accounts and were called 'c*nts' on the phone. Will you join me in condemning this outrage.”
The MP, who faces expulsion from Labour at a forthcoming disciplinary hearing over his repeated interventions in the party's antisemitism crisis, also circulated a message allegedly sent to the event’s organiser Greg Hadfield by the hotel’s management.
The message claimed staff had been “subjected to abuse and threats” and that they had cancelled the event because “guests and employees” would be put “at potential harm”.
Mr Hadfield has previously been suspended from Labour himself over allegations of bullying and intimidation. In May, he was accused of supporting a suspended Labour candidate who had posted a series of antisemitic tweets.
The event was also due to host the auctioning of a cartoon by Steve Bell that The Guardian refused to publish last month.
The cartoon depicts Labour deputy leader Tom Watson as an "antisemite finder general" for being critical of Jew-hate in the party.
Mr Watson encounters Israeli Prime Minister Benjamin Netanyahu and calling him an "antisemitic trope" only to apologise saying "I thought you were a member of the Labour Party".
The JC published the cartoon in full after Mr Bell sent it saying: "Please feel free to publish them as the Guardian don’t wish to, for reasons which still remain unclear to me and, I think, to them."
