The refusal of Amanda Serrano to compete in an undisputed featherweight fight because of issues over 12-round contests is “frustrating”, says WBC champion Skye Nicolson.

Serrano vacated her WBC title in December after the organisation refused to sanction fights of 12 three-minute rounds.

Women’s bouts are usually contested over 10 two-minute rounds.

The other major governing bodies – the IBF, WBA and WBO – now allow contests of 12 three-minute rounds, and Serrano retained those titles by beating Danila Ramos over 36 minutes last October.

Australian fighter Nicolson claimed the WBC featherweight belt earlier this month, comprehensively outpointing Sarah Mahfoud in Las Vegas, and called out Serrano for a unification bout afterwards.

Serrano, who has 46 wins from 49 professional fights including 30 knockouts, is one of the greatest female fighters of all time.

But Nicolson criticised her for her stance on the WBC’s rules, adding that the other governing bodies have “opened up a can of worms” by allowing longer bouts.

“Of course it is frustrating, all the other females are fighting 10 two-minute rounds, and she’s just come out and said, ‘this is what I want to do and what I am doing’,” Nicolson told BBC Sport.

“The other sanctioning bodies allowing that has caused a disruption in our division – now there isn’t an undisputed champion, it is very hard to make an undisputed fight when she does not want to abide by the rules that are set for everyone.

“I have no problem fighting 12 three-minute rounds, if that was the only way of fighting her I would do it. But I want to be undisputed.”