The 23-year-old actress, known for her roles in "Pride & Prejudice" and "Domino," said the upcoming movie is not about the popular royal family member, but rather follows the life of Georgiana, duchess of Devonshire, The Sunday Times of London reported.

"I am Georgiana," Knightley said. "I am not Diana. The film is not about Diana."

"The two were related by ancestry and united by destiny" a voice in the trailer says in reference to an inserted clip of the late princess. "History repeats itself."

The author who wrote the biography upon which "Duchess" is based, has echoed Knightley's comments.

"There is absolutely no reason to have done this trailer, which is a bad joke," Amanda Foreman told the Times.

"The marketing people probably thought the only way they could get the young popcorn-eating brigade to see this film was if they made some comparison with Diana. But they did not need to and should not have done it."