Floyd Mayweather has accused Conor McGregor of making a series of alleged racial slurs that included insults directed at his family.
Mayweather rounded on his rival at Wembley Arena in the final leg of their four-date world tour to promote their boxing bout at the T-Mobile Arena in Las Vegas on August 26.
McGregor is alleged to have made the comments in the early hours of Friday morning during the third stop of the tour in New York.
"I respect every country. Racism still exists. It's all about treating people like you want to be treated. To get respect you must give respect," Mayweather said.
"He totally disrespected black women. He called black people monkeys. Then he spoke disrespectfully to my mother and he spoke disrespectfully to my daughter.
"I'm not going to stoop that low and speak about his like or speak about his child. I'm glad that he just had a healthy child and he has a beautiful family.
"There are certain levels you don't stoop to and certain levels you just don't go to. I love everybody from all walks of life."