(TMZ) Nine black former "American Idol" contestants -- from various seasons -- are banding together to SUE the show ... claiming they were all FORCED off "Idol" as part of a racist (and illegal) plot to boost ratings. 

TMZ has obtained a letter, submitted to the U.S. Equal Employment Opportunity Commission by NY attorney James H. Freeman -- in which he asks for permission to sue Idol and FOX on behalf of his clients ... who have all appeared on the show:   FYI, Freeman is required to file with the EEOC before filing suit.

Corey Clark (Season 2), Jaered Andrews (Season 2), Donnie Williams (Season 3), Terrell Brittenum (Season 5), Derrell Brittenum (Season 5), Thomas Daniels (Season 6), Akron Watson (Season 6), Ju'Not Joyner (Season 8) and Chris Golightly (Season 9). 

In his letter, Freeman claims he noticed something fishy about "Idol" when Jermaine Jones was kicked off on March 15, 2012. Producers had claimed Jones failed to inform them about multiple outstanding warrants out for his arrest.  

Read more: TMZ