Unite general secretary Len McCluskey has said critics of Jeremy Corbyn used the issue of antisemitism within Labour in order to undermine him.
The union boss branded critics who sought to use antisemitism as "despicable" but added that the party "never handled the antisemitism issue correctly."
Speaking to the BBC's Andrew Marr Show on Sunday, Mr McCluskey said: "I'm absolutely convinced that there were those individuals who opposed Jeremy Corbyn's election right from the beginning, used the antisemitism issue - which I think is quite despicable that they did this on such an important subject - to undermine Corbyn, there's no doubt about that."
He added that the party had "never handled the antisemitism issue correctly” and that "we should have done things quicker."