Charlie Edwards has vacated his WBC flyweight title after expressing concerns about making 112lbs during his controversial no-contest against Julio Cesar Martinez five weeks ago.
Martinez was declared the winner by third-round knockout on the undercard of Vasyl Lomachenko-Luke Campbell on August 31, but replays showed the final blow came after Edwards had already taken a knee.
The result was therefore overturned as Edwards retained his crown and, although WBC president Mauricio Sulaiman said moments afterwards that "a direct rematch will be ordered", the Londoner has decided to move up in weight.
In a letter to Sulaiman, Edwards wrote: "It actually scared me about how much I was putting my health on the line and I can't risk causing damage to myself as health is the single most important thing in life.
"I am gutted because I value being WBC world champion and so proud to be able to be in history as WBC flyweight world champion.
"I want to continue to represent the WBC and really, really want to push on through the super flyweight rankings and persuade (sic) the super flyweight title.
"But I wanted to let you know first before anyone else that I will be vacating the title to move up and challenge at the new weight."
Edwards, who has won 15 of his 17 professional contests, became world champion with a unanimous decision win over Cristofer Rosales in December last year before comfortably outpointing Angel Moreno in March.