Aaron Cook feels he has been "robbed" of an Olympic taekwondo place and is considering taking his fight to the Court of Arbitration for Sport.
The world number one, 21, said he broke down in tears after being told Lutalo Muhammad had been chosen instead.
Muhammad was nominated by GB Taekwondo to fight in the under-80kg category.
Cook said: "I feel like I've been cheated, I've been robbed, and I've got to do all I can to try to get myself onto that mat in London."
Speaking to Victoria Derbyshire on BBC Radio 5 live, Cook added: "When I got the news, I was extremely upset. I started crying and I didn't know what to do."
Asked if he would consider taking his case to the Court of Arbitration for Sport, he replied: "Yes. My lawyers are looking into what's the next step. There could be a chance to go legal and if that's the right move, then that's what the next step is going to be.
"But we'll have to wait and see on that."
Muhammad, 21, has stepped down from the under-87kg category, in which he won a European title in Manchester earlier this year.
But he is ranked 58 places below Cook in the under-80kg class.
Gary Hall, GB Taekwondo's performance director, has described the Cook camp's attempts to get Muhammad's selection overturned as "desperate".
But Cook said: "Well, this is Gary Hall and GB Taekwondo's views. They're bringing the sport into disrepute, I think."