The intervention comes after Lord Jonathan Sacks branded the Labour leader an “anti-semite” and compared Mr Corbyn’s comments on Zionists to Enoch Powell’s inflammatory “rivers of blood” speech.
During a tour of Africa, Mrs May said: “Anti-semitism is racism. We should all condemn racism in all its forms.
“Lord Sacks was a long-standing chief rabbi. He raised significant concerns, but it’s not just him – members of the Labour Party have raised concerns as well.
“I think the leader of the Labour Party needs to respond to those concerns.”