Julia Roberts pulled out of shooting the Oscar-winning film "Shakespeare in Love," one of the film's producers said.Frank Edwards/Fotos International/Getty Images, Universal Pictures

Julia Roberts was originally cast in "Shakespeare in Love" but struggled to do a British accent.

A producer wrote in an essay for Air Mail that Roberts quit after she sensed his "unease."

Gwyneth Paltrow took the role, but the recasting is said to have cost the production millions.

Julia Roberts pulled out of shooting the Oscar-winning movie "Shakespeare in Love" after one of the film's producers criticized her attempt at a British accent, the producer said.

The producer, Edward Zwick, recently published a first-person essay for Air Mail all about the making of the 1998 film, which went on to gross nearly $300 million and took home seven Academy Awards, including best actress for Roberts' replacement, Gwyneth Paltrow.

Zwick recalled the difficulty he had getting the movie off the ground, saying Universal Pictures decided to back the project only when the "Pretty Woman" star signed on to play the film's heroine, Viola de Lesseps.

But Zwick said that as Roberts was set on having Daniel Day-Lewis — who was unavailable — play opposite her as the titular bard, she ended up "sabotaging" her chemistry reads with the bevy of up-and-coming actors Zwick considered for the role, including Hugh Grant, Colin Firth, and Sean Bean.

"Julia found fault with all of them: one was stiff, another wasn't romantic, and so on," Zwick, who also directed "Legends of the Fall," recalled.

Gwyneth Paltrow and Joseph Fiennes were eventually cast in "Shakespeare in Love."Miramax

Zwick said that after Day-Lewis reiterated that he couldn't play the part, as he was committed to filming another movie, "In the Name of the Father," Roberts reluctantly read opposite Ralph Fiennes, whose brother Joseph Fiennes would eventually land the part.

Zwick said that it went disastrously and that two weeks went by before Roberts agreed to test with the actor Paul McGann.

Zwick said that was when he realized Roberts wasn't cut out for the role — despite receiving lessons from the dialect coach Joan Washington, she couldn't do a convincing British accent.

"On the morning of the test, Julia emerged from makeup, looking radiant in full period costume," he wrote.

"But once she began to say the words, something was wrong. There was no magic. The problem wasn't the script. Or Paul McGann. It was Julia. From the moment she began to speak it was clear she hadn't been working on the accent," Zwick said.

The producer added, "Sensing Julia's discomfort, I tried to be encouraging, but she must have intuited my unease, and I made the tragic mistake of underestimating her insecurity.

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Roberts and Ralph Fiennes, pictured at the Tony Awards in 2006, had a disastrous chemistry read, Edward Zwick said.Kevin Mazur/Getty Images

"Having only recently been catapulted to the dizzying heights atop the Hollywood food chain, she must have been terrified to fail," he continued. "But I would never get to talk her off the ledge. The next morning when I called her room, I was told she had checked out."

Zwick also said the actor was going through a difficult period in her personal life, having recently called off her wedding to Kiefer Sutherland.

He added that at the time she was "shacking up" with the actor's close friend Jason Patric, which became tabloid fodder.

Zwick wrote that Roberts' manager confirmed to him that Roberts "had flown back to the US and that she was leaving the project." He described it as a massive blow, as he learned from Tom Pollock, the head of Universal at the time, that the company had already spent $6 million on the project.

"I've never spoken to Julia again," Zwick wrote. "Instead, I've observed from afar as her work grew in depth and stature. I bear her no ill will."

Representatives for Roberts did not immediately respond to a request for comment.