Serena Williams insisted she was not cheating in the US Open final on Saturday before accusing the sport which has made her a global icon and multi-millionaire of sexism.

Naomi Osaka won the final 6-2, 6-4 to become Japan’s first ever Grand Slam singles champion and delay Williams’s bid for a record-equalling 24th major title.

However, the final was overshadowed by the American’s angry and tear-filled tirade in the second set.

It has already been dubbed ‘The Mother of all Meltdowns’ by the New York Daily Post.

The 36-year-old was handed a code violation for coaching, a penalty point for racquet abuse and a game penalty for calling umpire Carlos Ramos a “liar and a thief” and insisting “you owe me an apology”.

“He alleged that I was cheating, and I wasn’t cheating,” Williams told reporters later.

“I don’t use on-court coaching (where it’s allowed at WTA tour events).

“One thing I love about tennis is being out there. It’s the one time I don’t want to hear anyone tell me anything. You have to figure out. You have to problem-solve.”

Williams said that her coach Patrick Mouratoglou had not been coaching her even though the Frenchman told ESPN that he had and that all coaches do it.

“I just texted Patrick, like, What is he talking about? Because we don’t have signals. We have never discussed signals,” said Williams.

Williams said the incident strengthened her belief that women players are treated differently to their male counterparts in the sport.

“I’ve seen other men call other umpires several things. I’m here fighting for women’s rights and for women’s equality,” she claimed.

“For me to say ‘thief’ and for him to take a game, it made me feel like it was a sexist remark.”

“He’s never taken a game from a man because they said ‘thief’. For me it blows my mind. But I’m going to continue to fight for women.”

Williams made reference to the incident last week when French player Alize Cornet was warned for removing her shirt on court during a heatwave.

Cornet was accused of “unsportsmanlike behaviour” before tournament chiefs apologised, admitting the umpire made the wrong decision.