The Australian Shooting Association (ASA) arranged a three-stage shoot-off between Nathan Cassells and Olympic champion Michael Diamond for the second single trap spot after Diamond missed official qualifying.

But Cassells, who finished second in the Australian trials, is taking legal action to stop the shoot-off, claiming it is in breach of selection rules.

"It's nothing personal against Michael at all. There'll be no nastiness," Cassells told reporters.

"I know that everyone who could have been in my shoes was going to do exactly the same thing."

The ASA agreed to the shoot-off on the recommendation of the Australian Olympic Committee after Diamond missed selection.

Diamond, who won gold at the Atlanta and Sydney Olympics, was prevented from competing in the first round of qualifying trials in January after he had his gun licence suspended following charges of assaulting his former girlfriend and failing to properly store his firearms.

Police returned his licence earlier this month when he was found not guilty of the charges and the ASA threw him a lifeline for Olympic qualification by agreeing to a shoot-off with the eventual runner-up.

Cassells, a former junior world champion, said he would still compete against Diamond next week regardless of the outcome of his legal action.