John Carney, the director of Sing Street, Once and the Bachelors Walk TV series, has issued an unreserved apology to Keira Knightley for comments he made about the British star in a recent interview.

Posting on Twitter on Wednesday night, he wrote that he was “ashamed” of the comments he had made during an interview with the UK Independent about his experiences working with Knightley on the set of Begin Again, a musical romantic comedy co-starring Mark Ruffalo and Adam Levine.

In the film, released two years ago, Knightley plays a young singer-songwriter who forms a bond with disgraced music executive Ruffalo in New York.

“Keira has an entourage that follow her everywhere so it’s very hard to get any real work done,” Carney had told the Independent, saying that he had learned from the experience “that I’ll never make a film with supermodels again,” and adding that “Keira’s thing is to hide who you are and I don’t think you can be an actor and do that (...) 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.”

Since the interview was published last Saturday, a number of high-profile film-makers have defended Knightley and criticised the Irish director.

“My experience with #keiraknightley was utterly spectacular on every level,” Mark Romanek, director of Never Let Me Go, tweeted.

“I have no clue what this guy is talking about. #arrogantshithead”. Vanity Fair commented that “after the public drubbing he gave Knightley, many actors may feel shy about opening up for Carney in future”.

“Recently in a phone interview, the conversation turned to a discussion about a past film, Begin Again, starring Keira Knightley,” Carney said in his statement on Wednesday.

“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 who I have offended. It’s not something that I could ever justify, and will never repeat.”

Carney had been speaking to the Independent as part of his promotional duties for the UK release of Sing Street, his Dublin-set coming-of-age musical drama which was released in Ireland earlier this year.