The veteran actor, who walked out of the jungle on Monday, mocked Opik for having the "mental age of 7" and branded him "insane".
"Not for one second could I imagine how he could be a member of parliament for 13 years," said the 59-year-old. "He thinks he's going to be the mayor of London at the moment. Ha!"
Havers continued: "I nearly killed him one day. We only had two knives in the camp - one was big and one was small. He was whittling a piece of wood and I shouted at him, 'Don't do that'. He said to me, 'What do you mean?' I said to him, 'You’re blunting the f**king knives'.
"That's one of the reasons I thought I should go because I would've killed him."
> Click here for our full chat with Nigel Havers