WATCH: 'You can't even read' - Conor McGregor pokes fun at Floyd Mayweather's much-rumoured illiteracy
Conor McGregor is proving he is easily a match for Floyd Mayweather - outside the ring at least.
Facing off against the American in the second round of their media tour ahead of next month's much-anticipated fight, the Irishman pummeled the undefeated former five-weight world champion with insults.
The 28-year-old joked again about Mayweather's tax problems and even took a swipe at Mayweather's much-rumoured illiteracy.
Even Mayweather, booed throughout, knew McGregor was winning the heart and minds battle.
Mixed martial arts star McGregor has never boxed professionally, but will take on Mayweather in Las Vegas on August 26 under normal boxing rules.
The pair are promoting the fight across four cities in as many days, but after McGregor's microphone appeared to be cut as Mayweather spoke in Los Angeles on Tuesday, the Irishman declared to a raucous crowd of 16,000 in Toronto: "Does this mic work? Then f*** that mic."
Addressing Showtime executive vice president Stephen Espinoza, he added: "F*** Showtime too you little weasel - I can see it in your eyes that you're a little b****.
"Cut my mic off? Cut the champ's mic off? Hell no.
"They're trying to throw me off and set me in an uncomfortable position but I thrive in uncomfortable positions.
"I'm 28 years old and I'm getting fight cheques and promoter cheques. When Floyd was 28 he was on Oscar de la Hoya's under card.
"Floyd is an old, weak b****.
"He's never fought a day in his life; he's a runner, he's boxing's biggest b****."
Mayweather was booed throughout by the crowd, who chanted "pay your taxes" at the American in response to reports the 40-year-old still owes the Internal Revenue Service millions of dollars from his 2015 fight against Manny Pacquiao.
After poking fun at Mayweather's tracksuit in LA, McGregor again mocked what Mayweather was wearing.
“You’re 40 f***ing years of age. Learn to dress,” McGregor said. “You’re carrying a schoolbag on stage. What do you need a schoolbag for? You can’t even read!”
Responding to a McGregor quip that he cannot read, Mayweather - who had produced a cheque 100million US dollars on Tuesday - said: "They said I'm the mother f***** that can't read: I do numbers, I make money."
McGregor responded: "You owe money".
At one point Mayweather took an Irish flag from the crowd and draped himself in it - prompting McGregor to open Mayweather’s backpack. Claiming to find cash in it, he said: “$5000, that’s it?”
Mayweather acknowledged the crowd's support for McGregor, but said he was not fazed by this".
“The fans can’t fight for him ... I’ve been through this so many times.”
The media tour continues in New York on Thursday, before the pair appear in London on Friday.