Labour peer Lord Alan Sugar has told Londoners not to vote for his party's candidate in the mayoral election, despite him having the backing of the party's leader.
"I don’t care if Ed Miliband is backing Livingstone. I seriously suggest NO ONE votes for Livingstone in the Mayoral elections," he wrote on Twitter.
"Sky doing live Mayoral interview with candidates at 8pm today Johnston v Livingstone is real issue. Livingstone must NOT get in on 3rd May," he tweeted to his 1.9 million followers.
The star of The Apprentice also dismissed suggestions that he should take on the role himself.
"It's been suggested I run for Mayor. Not possible, too many commercial conflicts, no time, more to the point I would not know where to start," he said.
It is not the first time Lord Sugar has criticised his own party. Last month he attacked Miliband for "jumping on the bandwagon of bank bashing".
Speaking during a debate on the Budget, Lord Sugar criticised Miliband's decision to condemn moves to award RBS chief executive Stephen Hester a bonus of almost £1m.
"The reality is carry on doing that and these people will go and get a job in a different type of company where the culture of paying bonuses is not frowned upon," he said.
"Pay peanuts and you will get monkeys," he said. "Change the record, start to install some confidence in the market place."