Kevin Phillips pulled a goal back from the penalty spot in the 80th minute after Jonathan Fortune had brought down Flo but it was much too little too late and the relegation trap-door looms large at the Stadium of Light.
Beaten at home in midweek by Southampton, the Black Cats could ill-afford to finish empty-handed again and if a return to the Nationwide League is to be avoided, there will have to be a vast improvement in the last dozen matches.
Sunderland had proved more than a match for the visitors until the 24th minute opener. Central defender Fish’s shot was deflected by Flo and full-back Stephen Wright applied the finishing touch.
In the 31st minute a left-wing corner eluded a ruck of players before the ball struck the hapless Proctor to give Charlton a remarkable three-goal lead.
Jason Euell missed two great chances early in the second half to rub salt into Sunderland’s wounds and though the home side kept battling to the end, pulling the game out of the fire was beyond their wildest dreams.