Daiki Kameda, who controversially retained his IBF super flyweight crown despite a defeat last December, said Wednesday that he is returning the belt.

"It's bad since I lost. This I admit," said Kameda at Narita airport before departing for training in the United States. "I apologize for causing trouble."

Kameda lost his unification title bout against Liborio Solis of Venezuela last December after Solis failed to make weight.

The International Boxing Federation had said prior to the bout that both titles would become vacant in the event Solis won, but inexplicably overturned its own rule and declared Kameda the IBF champion despite his defeat.

The ruling sparked a controversy with the Japan Boxing Commission, which claimed that the Kameda camp was negligent in reporting that its fighter could retain the IBF crown win, lose or draw, although it was aware of this fact in advance.

In February, the JBC announced it would not permit the renewal of licenses for Shinji Yoshii, the Kameda Gym's chairman, and its manager, Satoshi Shima, as a punishment for causing the confusion.

The JBC's measure effectively bans the three Kameda brothers from fighting in Japan unless the gym appoints a new chairman and manager.

The JBC said the same day it has received a letter of apology from the IBF, accepting full responsibility for causing the mix-up.

"The IBF frankly recognized that the JBC was not to blame," JBC chairman Hiroshi Akiyama said at a news conference in Tokyo. "It's best that this type of situation be quickly resolved. To some extent, I want to commend the Kameda camp (for returning the belt)."

Lindsey Tucker, an IBF supervisor who was in charge of setting the rules for the fight, will not be allowed to supervise fights in Japan for the immediate future.