The former 'Lost' actress plays elf character Tauriel – who has been created for the film and is not a part of the original book by J.R.R. Tolkien – and is worried about how die-hard fans will react to the role.

She told SFX.co.uk: "I am very concerned to this day that people will watch it and I'll be the black mark on the film.

"I know how adamant the purists are, and I'm one of them!"

She does, however, feel that director Peter Jackson is right to add her part to the movie – a two part prequel to 'Lord Of The Rings' - and assures that all the additional characters he has added stay true to the ideals created by Tolkien.

She added: "Upon reading 'The Hobbit' again, as an adult, I can see why additional characters were needed to round out the story as an adaptation -especially female characters.

"'The Hobbit' didn't include female characters at all. What they have done is all in perfect keeping with Tolkien's world, while adding a third dimension to an otherwise very two-dimensional story."

The first film, 'The Hobbit: An Unexpected Journey', will be in cinemas this December.