The party's failure to adopt the full International Holocaust Remembrance Association (IHRA) definition of antisemitism, opting instead to omit key examples it gives of how criticising Israel can be antisemitic, has triggered a standoff with its Jewish MPs and supporters.
Speaking at the book festival, Mr Brown said: “Jeremy Corbyn has got to change. He cannot sustain particularly what he is saying about the international agreement on what we do in our attitudes to both the Holocaust and to Israel.
“I predict to you that’s going to change within a few weeks. I believe that it will change but even that will not be enough.
“You have got to show by your actions, not simply by saying some words – that you understand the deep hurt that has been caused. I’m very clear about that.
“We have a problem in Britain, not just with Islamophobia and not just with racism against the black community. We have a problem within the Labour party with antisemitism and it has got to be dealt with.
“This cannot keep going on as a running sore, and it’s not because it’s an embarrassment, it is because it is simply wrong.”
The Guardian is also reporting that the party is preparing to adopt the IHRA definition of antisemitism in full – provided that it can allow for legitimate criticism of Israel.
The Unite, Unison and GMB unions, which donate millions of pounds to the party each year and hold significant influence, have publicly pushed for the adoption of the full definition.