The 26-year-old star admitted that he relies on changing the way he speaks to feel like he is in character.
He told The Sun: "I feel very naked with my British accent. I feel like I'm not really acting."
However 'The Twilight Saga: Breaking Dawn - Part 2' actor confessed that he doesn't have much interest in starring in movies based in the United Kingdom as the American film industry is far superior.
He added: "And also, English things aren't very good."
Robert recently revealed he isn't "buff enough" to be an action star.
The hunk admitted he would prefer to make smaller, gritty dramas rather than take on blockbuster roles because he thinks he doesn't have the physique to be an action hero.
He said: "If there is a way to maintain a career doing small, interesting movies I would take that option. I'm not buff enough for robot movies."
He told Empire magazine: "That's my biggest problem, confidence. I'm taking baby steps and hoping people will keep employing me. I can't see tons of people watching 'Cosmopolis' and screaming at it. It would be amazing if they did."