John Carney has publicly apologised for slamming Keira Knightley.

Keira Knightley

Keira Knightley

During a recent interview the 'Sing Street' director launched an attack on Keira, who starred in his 2013 movie 'Begin Again', blaming her for the movie's shortcomings but after a massive backlash he took to Twitter to admit he was "petty, mean and hurtful".

In a post he captioned: "From a director who feels like a complete idiot," John wrote: "Recently, in a phone interview, the conversation turned to a discussion about a past film, Begin Again, starring Kiera Knightley. I said a number of things about Keira which were petty, mean and hurtful. 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. It's arrogant and disrespectful. Keira was nothing but professional and dedicated during that film and she contributed hugely to its success. I wrote to Keira personally to apologise, but I wanted to publicly and unreservedly apologise to her fans and friends and anyone else I have offended. It's not something that I could ever justify and will never repeat (sic)."

John blasted two-time Oscar nominee Keira's acting skills in his recent interview and described his new movie as "a small personal movie with no Keira Knightleys in it".

He said: "I learned that I'll never make a film with supermodels again ... I like working with actors and I wanted to come back to what I knew and enjoy film-making again -- not that I didn't enjoy Begin Again, but Keira has an entourage that follow her everywhere so it's very hard to get any real work done ... Keira's thing is to hide who you are, and I don't think you can be an actor and do that ... I don't want to rubbish Keira, but you know it's hard being a film actor and it requires a certain level of honesty and self-analysis that I don't think she's ready for yet and I certainly don't think she was ready for on that film."

However, he faced an immediate backlash and a number of directors, who have worked with the 31-year-old actress, rushed to defend her.

Mark Romanek, who worked on 'Never Let Me Go' in 2010 with Keira tweeted: "My experience with #keiraknightley was utterly spectacular on every level. I have no clue what this guy is talking about. #arrogants**thead

"My recollection of #keiraknightley's "entourage" was that her mum visited the set one day for an hour or two (sic)."

Lorene Scafaria, director of 'Seeking a Friend for the End of the World', tweeted: "I agree with Mark. Keira was a joy to work w/. Present & easy & really, really good at her job. Just lovely (sic)."

And Lynn Shelton from 'Laggies' added: "Working with #KeiraKnightley was magnificent, top to bottom. She is the real deal. #Knightleylove (sic)."

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