The board also criticised Corbyn's latest video, accusing him on Twitter of "painting Labour's problem as a regrettable statistical matter," rather than an "inevitable outcome of a political culture to which he has contributed."
Just as in the Guardian, Corbyn failed in the video to address whether the party will accept in full the IHRA definition of antisemitism.
The party has proposed adopting most of the definition, while rejecting specific examples of antisemitism referring to Israel.
The leader also made no mention of disciplinary proceedings against two Labour lawmakers over their criticism of his handling of the row.
Jewish MP Margaret Hodge and Ian Austin, whose adoptive parents lost relatives in the Holocaust, are both being probed by party authorities after criticising Labour's failures to stamp out antisemitism.
Deputy Party Leader Tom Watson - who has had a difficult relationship with Corbyn - used an interview with the Observer to call for those investigations to be called off, and for the party to adopt the full IHRA definition.
"This is one of those moments when we have to take a long, hard look at ourselves, stand up for what is right and present the party as fit to lead the nation - or disappear into a vortex of eternal shame and embarrassment," Watson told the paper, which is affiliated with the Guardian. "It is very important that we all work to de-escalate this disagreement."
- Bloomberg