Undisputed featherweight world champion Amanda Serrano has announced she is relinquishing her WBC title after the governing body refused to sanction fights of 12 three-minute rounds.
The Puerto Rican retained her WBO, WBA and IBF belts in October with victory over Danila Ramos in a contest fought over that length.
However, her WBC title was not on the line because the organisation did not endorse the format.
Women's fights are typically fought over 10 two-minute rounds.
Serrano wrote on Instagram: "Moving forward if a sanctioning body doesn't want to give me and my fellow fighters the choice to fight the same as the men, then I will not be fighting for that sanctioning body.
"The WBC has refused to evolve the sport for equality. So I am relinquishing their title.
"Thank you to the sanctioning bodies who have evolved for equality!"
WBC President Mauricio Sulaiman had earlier said that they would not sanction 12 three-minute rounds in women's bouts.
"Tennis, women play three sets. Basketball, the basket is shorter and the ball smaller and those are not contact sports. We stand by safety and well-being of the fighters," Sulaiman wrote on X, formerly Twitter, in September.
Both Serrano and Ramos were able to compete under the new rules without damage or incident, Serrano wrote on X.
"It's something I’ve wanted for years and finally now that I’m in the position, I will continue my career under that rule," she added.
Serrrano has raised the possibility of a rematch with Katie Taylor in Ireland next summer.
The initial second bout was postponed due to injury, leading to Chantelle Cameron becoming Taylor's next opponent.
The Bray boxer won a memorable initial clash with Serrano in April last year.
