"Sometimes in life, you think you found the one. But then one day you find out, that she is just some [expletive]!" Hollywood Life quoted Timberlake as saying at this past Saturday's concert as he introduced his breakup anthem, "Cry Me a River."
The remark was met with a backlash online from fans who thought he was trash-talking Spears, who can be heard saying, "It's Britney, [expletive]," in two of her hit songs -- "Gimme More" and "Scream & Shout."
"Ok. I see you. Wouldn't disrespect ANYONE personally. Ever. #Relax #ItsBritney[Expletive] I do love that saying though*with accent* #Respect," Timberlake tweeted to upset fans.
The couple dated for three years and broke up in 2002. Spears went on to have two sons with her now-ex-husband Kevin Federline.
Timberlake is now married to actress Jessica Biel.