Producers at film company Pathe have started work on the project and are keen to cast the 'Pirates Of The Caribbean' star as Diana, with Dame Helen Mirren as her mother, Frances Shand Kydd, reported Daily Mail online.

But the 25-year-old will face stiff competition from Hollywood beauty Scarlett Johannson, who is also in the fray for the role.

Next year's release date has been timed to coincide with what would have been the Princess's 50th birthday. The year also marks 30 years since Diana's wedding to Prince Charles.

"The project is in the early stages but Pathe has chosen 2011 quite deliberately," a source said.Mirren's success in 'The Queen', also made by Pathe, has led to the star being earmarked to play Diana's mother.

The film will chart the early years of Diana's life, her ill-fated marriage to Charles, their separation and her death in Paris in 1997.

"They think Keira will be perfect to play Diana. It will be in the same vein as their movie The Queen and will detail the ups and downs of Diana's marriage and the early lives of the Princes," said the source