Skyfall star Whishaw was tapped as the frontrunner to take over from comedian Sacha Baron Cohen as the flamboyant frontman in October (13), and now his involvement has been confirmed by executives at production firm GK Films.
Sacha Baron Cohen quit the project in July (13), citing "creative differences".
Lock, Stock and Two Smoking Barrels actor Fletcher will helm the as-yet-untitled project after impressing movie bosses with his directorial debut, the critically-acclaimed Wild Bill, in 2011, and his subsequent Sunshine on Leith project, a film adaptation of the hit musical featuring the songs of The Proclaimers.
Surviving Queen members Brian May, Roger Taylor and John Deacon will serve as co-producers on the long-awaited Mercury film, which was originally scheduled for release in 2012.
Mercury died from an AIDS-related illness in 1991.