Jeremy Corbyn and John McDonnell both backed a bid to rename Holocaust Memorial Day "Genocide Memorial Day" - something the educational pamphlet they have just issued on anti-Jewish racism warns is "profoundly antisemitic".
On Sunday, Labour staged a high-profle launch of No Place For Antisemitism - a series of guidelines released on the party's own website and through a widely distributed leaflet.
Outling the tropes of antisemitism, it says: "The Holocaust's unique horror must never be minimised; Holocauast denial and revisionism are profoundly antisemitic."
But the JC can reveal that in 2011 an initiative entitled Never Again For Anyone was tabled in the House of Commons with Shadow Chancellor Mr McDonnell as its primary sponsor.
Also sponsoring the motion was the now Labour leader Mr Corbyn.
The Never Again For Anyone motion noted that "disabled people were the first victims of Nazi mass murder" and that "Nazism targeted not only Jewish, but also Roma, Jehovah's Witnesses, lesbian, gay and bisexual people and others deemed undesirables."
Calling for Holocaust Memorial Day to be renamed Genocide Memorial Day - Never Again For Anyone it declared that "every life is of value."
The motion was tabled on Holocaust Memorial Day itself.
One furious source who spoke to the JC on Monday said: "John McDonnell and Jeremy Corbyn have breached their own guidance on antisemitism.
"Today we are advised that denial, revisionism and minimisation constitutes antisemitism, yet in 2011 they were guilty of it through this disgraceful EDM.
"Maybe if the Labour Party had engaged with the Jewish community rather than mansplaining what is antisemitic, we would not be in this sorry situation.
"The irony is not lost on any of us."
No Place For Antisemitism was issued to party members on Sunday.
It was accompanied by an email from Mr Corbyn, in which he wrote: "We must face up to the unsettling truth that a small number of Labour members hold antisemitic views and a larger number don't recognise antisemitic stereotypes and conspiracy theories.”
The Jewish Labour Movement said the attempt by Labour to produce the resource to tackle hate was "too little, far too late."
A Labour spokesperson said:“This claim is false and illogical. Recognising other genocides does not minimise the horror of the Holocaust nor is it Holocaust denial or revisionism.”
