Asked to sum up Corbyn in less than 30 words, Johnson quipped he was: “A Chavez-admiring curiously-vested leader of a sleeper cell of crypto-communists who piratically captured the Labour Party.”

The former Mayor of London added he would be “deeply ashamed” if Corbyn was elected Prime Minister on June 8.

Asked how he would feel, Johnson replied: “Deeply shocked. I will feel deeply ashamed. Because I will feel we have somehow failed to explain the risk and that will be my fault.”