Alan Sugar pointed his accusing finger yesterday at Labour's candidate for the London mayoralty, Ken Livingstone, and told him, in so many words: "You're fired!"
The ex-Mayor has had a rocky few weeks as he tries to prise Boris Johnson out of his job. Yesterday, it was revealed that he pays a private firm for his annual medical check-ups – reinforcing allegations of double standards.
Lord Sugar made it very clear that despite being a Labour peer, he wants to see the Labour candidate defeated in the most important electoral contest of the year – though he did not say why.
He wrote on Twitter: "I don't care if Ed Miliband is backing Livingstone. I seriously suggest NO ONE votes for Livingstone in the mayoral election."
It is a setback for Mr Livingstone because Lord Sugar has 1.8 million Twitter followers, many of them young. Thousands more will have seen the message retweeted.
Members of the Labour Party risk automatic expulsion if they back another candidate against Labour in an election – but party officials made it clear yesterday that Lord Sugar has not fallen foul of this rule.
"There is a long history of Lord Sugar and Ken Livingstone not being the best of friends," a source said. "Lord Sugar was not recommending people vote for any of Ken's opponents."
It is not the first time that a Labour politician has drawn Alan Sugar's fury. Just before the 1992 general election, he filled a whole page of The Sun with a furious attack on Gordon Brown, who was then shadow Chancellor. It began: "I do not know who Gordon Brown is. Excuse my ignorance, but I don't."
Later he became firm friends with Mr Brown, who made him a Labour peer in 2009.