Veteran Labour MP Sir Gerald Kaufman is under attack for incendiary comments about a fellow Jewish MP during Wednesday's debate on universal jurisdiction.
Sir Gerald turned to a neighbour on the Commons green benches, as pro-Israel MP Louise Ellman rose to speak, and muttered: "Here we are, the Jews again".
The MP for Manchester Gorton is known for his strong anti-Israel views. After Operation Cast Lead in Gaza, he compared the actions of Israeli soldiers to the Nazis who forced his family to flee Poland.
He made the remark, heard by a number of MPs, during the report stage of the Police Bill, after Mrs Ellman had intervened during a speech by Anne Clwyd promoting an amendment to block the reform of universal jurisdiction.
Mrs Ellman confronted her colleague outside the chamber after the debate, to tell him his remarks had been heard.
A furious argument ensued. Known to be deeply upset, she has since made a formal complaint to Labour Chief Whip Rosie Winterton.
Hendon MP Matthew Offord later raised the issue with Deputy Speaker Lindsey Hoyle.
Asked to comment, Sir Gerald said it was not the first time and would not be the last that he disagreed with Louise Ellman.
He added: "I can't remember whether I said it or not. I can't remember every comment I said under my breath."
Jennifer Gerber, director of Labour Friends of Israel, condemned the remarks. "It's deeply disturbing that Sir Gerald made this comment to a fellow Labour MP. The Labour movement has no truck with this sort of remark, no matter who makes it.
"I would have hoped that Sir Gerald would know better. I urge him to make a formal apology."
In a statement released by the Labour party Sir Gerald said: "I regret if any remarks I made in the chamber caused offence. If they did, I apologise."
But the Board of Deputies described Sir Gerald’s comments as grossly offensive and said: “His conditional apology suggests that he is more embarrassed at being caught out than by what he said.”
John Mann MP, chair of the All-Party Parliamentary Group Against Antisemitism said he had written to the Labour party asking what could be done to prevent similar comments in future.