A former aide to Jeremy Corbyn has claimed they overheard the Labour leader and other members of his staff describe Jewish MP Dame Louise Ellman as "the Honourable Member for Tel Aviv."
The Mail on Sunday alleged the "spiteful" jibe was frequently directed at Dame Louise because of her opposition to Mr Corbyn over his failure to tackle antisemitism.
The Liverpool Riverside MP is also vice-chair of the Labour Friends of Israel organisation - and frequently defended the Jewish State in the House of Commons.
A spokesman for Mr Corbyn said the claim that he had called Dame Louise 'the MP for Tel Aviv' was "a fabrication".
But the former aide alleged the slur was used against the 73 year old MP saying: "I was very surprised and when I asked other members of staff they said he often did it in private, though not to her face."
A second source also told the Mail On Sunday: "If her name crops up, or she appears on the office TV, they'll say, 'There she goes again, the Honourable member for Tel Aviv.' They can't stand her."
Responding to the claims Dame Louise said: "If this is correct, I am appalled that a potential Prime Minister would use language of this sort against one of his own MPs.
"To refer to me as the 'MP for Tel Aviv' is to challenge my loyalty to this country.
"A key part the internationally accepted code on anti-Semitism which the Labour Party wants to dilute specifically states it is anti-Semitic to accuse Jews of being more loyal to Israel than to their own country."
Dame Louise last week denounced Mr Corbyn for hosting a Holocaust Memorial Day event during which the Israeli government was compared to the Nazis and in 2016, and she backed a motion of no confidence in Mr Corbyn by rebel Labour MPs.
Last Tuesday at a Momentum meeting in Liverpool, the JC witnessed a speech by a Labour activist which suggested Jewish MPs were "foot soldiers" for Israel "trying to take our democracy away from us."
The speech, by a member of Sefton Central Labour Party, went unchallenged by pro-Corbyn MP Chris Williamson who also spoke at the event.