Conor McGregor lands low blow in press conference battle with Floyd Mayweather: 'You can't even read!'

McGregor went on the offensive in Toronto, and drew loud laughs from the raucous crowd when he began teasing Mayweather for not being able to read

Dana White seemed to enjoy McGregor's series of put-downs (Getty )

Undefeated boxer Floyd Mayweather is the heavy favourite to win his bout against mixed marital arts champion Conor McGregor but the Irishman again won the war of words at their media conference in Toronto on Wednesday.

A day after McGregor mercilessly mocked the American in Los Angeles to launch a four-day international promotional tour for their Aug. 26 fight, the flamboyant 28-year-old again went on the offensive, ridiculing Mayweather's attire and landing a low blow with a comment about his rumoured reading difficulties.

“How do I look,” McGregor asked the crowd, before taking a swipe at Mayweather's bag. “He’s 40! Dress your age, don’t go carrying a school bag onto the stage.

“What are you doing with a school bag on stage? You can’t even read.”

Mayweather, dressed casually for a second straight day in a t-shirt and cap while McGregor again wore a suit, did his best to counter.

“I’m the one that can’t read? I do numbers, I make money,” he said.

“You owe money,” McGregor responded, referring to reports that Mayweather this month asked the IRS for more time to pay his 2015 tax bill.

Mayweather, who holds a perfect 49-0 record, was jeered relentlessly but did not appear rattled.

At one point he grabbed an Irish flag from the crowd and posed in front of McGregor. When the flag was passed to the Irishman he tossed it back in the boxer’s face.