By Oliver Hotham
Alan Sugar hit out against his own party's candidate for mayor of London today, in a move which could see him rejected from Labour.
The peer told his two million followers on Twitter that Livingstone "must not get in on 3rd May" before urging them not to vote for him.
Lord Sugar's attack on Labour's candidate is leading many to question why he is not being expelled or suspended from the party.
Editor of Labour List blog Mark Ferguson responded in an article by saying that Lord Sugar "has not, technically, broken any of Labour's rules".
He added: "If we were to kick out every party member who has urged people not to vote for Ken, then Sugar, alas, would not be the only person expelled.
"And let's remember that back in 2010 Livingstone was selected comfortably by the party – and I don't remember Lord Sugar complaining then."
The entrepreneur and presenter of "The Apprentice", who was made a peer by Gordon Brown in 2009, is known on Twitter for his spats, most notably with television presenter Piers Morgan.
Lord Sugar was quick to emphasise that, as a resident of Essex, he cannot vote in the mayoral elections.