David Haye threw a punch at Tony Bellew and launched an astonishing verbal attack on promoter Eddie Hearn at a news conference to publicise the fighters' March 4 clash.
WBC world cruiserweight champion Bellew is stepping up to heavyweight to box his fellow Briton Haye at the O2 Arena in London, and the atmosphere on Wednesday was highly charged.
Amid 20 minutes of bickering, former two-weight world champion Haye called Bellew a "powder puff punching chump" before the pair had to be separated.
Bellew branded Haye "a joke" and said he was only fighting him "because he has blown the lot".
And Hearn, who will co-promote the clash, did not escape Haye's ire either.
"I've been out of the big, big fights for a while and while I've been away I've noticed that it's become the Eddie Hearn show," Haye said at the Dorchester Hotel in Park Lane, London.
"This gives me a chance to shut his mouth. You [Bellew] say I had a lot of demands, the only demand Eddie Hearn had was that his name came first on the posters.
"I can't remember his dad [Barry] putting his head in the camera like he does. He should be promoting his fighters not himself.
"After I take out this guy [Bellew] out I'm going to take out Joshua and shut down your business.
"I could go clubbing every night between now and the fight and get smashed every night and still knock you [Bellew] out.
"It's an easy night's work and I will end the fight when I want. If I want to punish you I will or if I want to end it in 30 seconds I will."
Haye, who also claimed Australian Lucas Browne turned down $2 million (£1.6m) to fight him, and Bellew had to be separated amid a scuffle as they posed for photographers.
Bellew, 34, is taking on Haye after one defence of his world title, a third round win against Haye's friend BJ Flores.
Haye, 36, has had two comfortable stoppage wins this year after over three years in exile. The Londoner reigned as WBA world heavyweight champion from 2009 to 2011 and Bellew says his best days are behind him.
"Let's stop calling his last two fights 'fights', they were more exhibitions," said Bellew.
"One of them called himself 'The Cobra' but should have been called a maggot and the other is the first boxer who learned to box on YouTube. It's only right those fights were on a comedy channel.
"His last real fight was five years ago and while he has been partying away I've been in the gym. The difference between him and me is that I love fighting and he hates it. But he has to fight.
"All the demands and stipulations he put in the contract were ridiculous. He's the biggest diva ever in boxing.
"He could have been fighting for the world heavyweight title but he's not, he's fighting me because he's skint."