Mino Raiola has claimed that Alex Ferguson branded him "a t***" during talks over a new contract for Paul Pogba in 2012.
Pogba left United to join Juventus after failing to reach an agreement over a new deal, with then-manager Ferguson later claiming that Raiola's attitude made negotiations futile.
The France international's agent says the offer put forward by United was derisory and has revealed Ferguson's fury as the talks reached an impasse.
Speaking to The Financial Times, he recounted the conversation that took place in Ferguson's office:
"Ferguson to Pogba: You don't want to sign this contract?
"Pogba: We're not going to sign this contract under these conditions.
"Ferguson to Raiola: You're a t***.
"Raiola: This is an offer that my Chihuahuas -- I have two Chihuahuas -- don't sign.
"Ferguson: What do you think he needs to earn?
"Raiola: Not that.
"Ferguson: You're a t***."
Pogba was linked with Real Madrid and Barcelona before he completed a world-record transfer back to United from Juventus in August for an initial fee of £89.3million.
Question marks were raised over Pogba's decision to move back to Old Trafford when the club could not offer Champions League football and had not won the Premier League since 2013.
Raiola, however, says the switch made perfect sense as United had a greater need for a player of Pogba's quality.
"I think you have go to the club that needs you. This club needed them," he said.
"Pogba could have gone to all the top clubs. But Real Madrid had just won the Champions League. He'd have been a trophy player there. Barcelona -- their three trophies are [Lionel] Messi, Neymar and [Luis] Suarez.
"What you see is the final result of years of sculpting. I spent two years working on Manchester United's deal with Paul."
Raiola also suggested that part of his cut from the transfer was related to Pogba's ownership rights, though he insisted it had nothing to do with the banned practice of third-party ownership (TPO).
"I have to see how I can phrase this in a way that Juventus cannot tackle me through the law," he said. "In this deal Juventus was not the only owner of the player's rights."
When asked if he would own stakes in his players' rights before TPO was banned by FIFA in 2015, he added: "Not often. But sometimes.
"[Pogba was] not TPO. Be careful with the legal definition of TPO. But let's say that in that case there was an upside for our side. And by our side, I mean the player's side."