Carney apologised for the "petty, mean and hurtful" things he previously said about the actress, reported Ace Showbiz.
"From a director who feels like a complete idiot. I said a number of things about Keira, which were petty, mean and hurtful," he wrote on Twitter.
"I'm ashamed of myself that I could say such things.. And I've been trying to account for what they say about me. In trying to pick holes in my own work, I ended up blaming someone else. That's not only bad directing, that's shoddy behaviour that I am not in any way proud of."
Carney landed in hot water for bashing Knightley's talent. According to him, it was hard to get any work done because there was an "entourage" following her around.
He also questioned the authenticity of her performance. Soon after his interview, a series of directors and fellow Hollywood star came to Knightley's defense.