Enzo Maccarinelli has teamed up with former trainer Enzo Calzaghe in a bid to get back to the top.
The 30-year-old lost his European cruiserweight title to Alexander Frenkel last year.
And it prompted calls for him to retire.
But the former WBO cruiserweight king has responded by dropping down to light-heavyweight - and announcing his intention of winning another world title.
In his corner will be former trainer Calzaghe, who helped guide him to his WBO world title.
"I was comfortably beating Frenkel, but I paid the price for my own stubbornness, I had been training myself, doing too many weights and not enough fitness work and I paid the ultimate price, people say I boxed well, but I didn't, the fight footage makes me cringe," Maccarinelli told local paper The South Wales Argus.
"Soon afterwards Enzo got in contact with me and I asked him if he'd like to train me again, if he'd be willing to come back to boxing and he said he only would for me.
"I asked Frank (Warren) and all credit to him, he gave me his blessing and said that with Enzo I was at my best and he wants to get me back to that level.
"I don't want to retire, I am a fighter in and out of the ring and I will fight to get myself back into contention and back into the big events in British boxing.