Vogue noted that some judges and other stars on the show commented on her appearance, with one choreographer encouraging her to be “more ladylike” and learn how to dance in six-inch heels.
“Back then, I was just trying to move into a space of myself,” Buckley said. “I really hope that a 15, 17, whatever-age woman never has to be brutalised quite like what happened on that show.
“But I didn’t recognise it fully at the time. I just felt it, which was difficult.”
In response, the BBC pointed to its policies to ensure a duty of care for all who work with the corporation, which it said had been strengthened over decades.
Anybody putting complaints or concerns to the corporation are treated with the utmost care and seriousness, the BBC added.
Buckley also revealed that, after appearing on the talent series, she turned down an offer to be the understudy for winner Jodie Prenger.
Instead, Buckley pursued her own trajectory in London’s theatre landscape, taking a job in Stephen Sondheim’s A Little Night Music at the Menier Chocolate Factory theatre.
But she struggled in the early part of her career, telling Vogue: “I was just lost. When you’re told, culturally, in different ways, that you have to kind of mould yourself into a shape that doesn’t naturally fit you, in some ways you incubate that messaging and then it becomes self-destructive.
“Once I realised that, my life goal has been to unravel myself from the sort of miseducation, from stories that don’t actually serve me, and just find life.”
Buckley is now widely predicted to win best actress for Hamnet at events such as the Golden Globes, Baftas and Oscars in the coming weeks.
She stars opposite Paul Mescal in the film, which is directed by Chloé Zhao and adapted from the novel by Maggie O’Farrell.
It follows the death of the 11-year-old son of William Shakespeare and his wife Agnes, which some believe led the Bard to write his play Hamlet.