Michael Diamond's fight for a shot at his third Olympic gold medal is far from over, with the man he beat in a shoot-off declaring he will challenge Diamond's place on the shooting team.

Diamond beat Nathan Cassells in two world cup events to win their shoot-off for Athens, which was organised after Diamond missed the selection trials due to a court case on assault and firearms charges.

He was cleared of assaulting his ex-girlfriend and freed without conviction on the firearm charge.

Cassells, a former junior world champion, decided earlier this week he would not appeal his omission from the Olympic team but changed his mind after talking to friends.

"I just saw a few things I probably didn't see before," he said.

"You sort of bust your a*** a fair while and to let it slip is a bit stupid I suppose.

"I'm going to appeal within the next 48 hours.

"The way I see it is I went through the right procedure and did everything I had to do to qualify."

Australian Shooting Association (ASA) chief Nick Sullivan said the appeal was likely to be held next week in either Canberra or Sydney before an independent panel.

The panel would be made up of a Queen's Counsel, a high performance manager from another Olympic sport and a fellow shooter from outside their discipline of clay targets.

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