Ex 'American Idol' Corey Clark -- I Got Railroaded By My Wife's Stepdad ... He's the Cop Behind My Arrest (VIDEO)

Former "American Idol" contestant Corey Clark's arrest was the result of a conspiracy -- set in place by his estranged wife and her detective stepfather ... at least that's what Clark is claiming now.

Clark got busted September 23 in Yuma, AZ, and was eventually charged with misdemeanor domestic violence. But Tuesday in L.A. he told us the whole thing was a revenge plot.

Clark says he'd filed a report against Monica Clark just prior to his arrest, claiming she was violating their child custody agreement. Clark thinks it's no coincidence he was arrested right after that, especially because his wife's stepfather is a Yuma PD detective.

We've reached out to Yuma PD for a response ... so far, no word back.