Momentum, the organization founded to help Corbyn become leader of the Labour Party, said that antisemitism is a real problem in the party and called for working hard to put an end to it.

The Shame of Antisemitism on the Left Has a Long, Malign History.

One of the bases of antisemitism was the practice of focusing on the fraction of plutocrats that were Jews, and disregarding the more numerous non-Jewish plutocrats who did the same things.