The 31-year-old actress has established herself as one of the most sought-after stage and screen stars in the world, yet Gemma believes her working-class background has been held against her in some instances.
She said: "I can only speak from my personal experience. There have definitely been times when I have not got jobs because it was thought I was not posh enough. I know that."
But Gemma also acknowledged the idea can be overplayed at times, pointing out that some actors from working-class backgrounds simply wish to steer clear of playing "posh" characters.
She told the Irish Times newspaper: "I think maybe it is a bit of a myth. Don't forget that actors choose. Not all actors want to play posh."
As well as starring in big-budget movies, like the James Bond film 'Quantum of Solace' in 2008, Gemma has also been hailed for her theatre work, which has included her widely acclaimed performance in the musical version of 'Made in Dagenham'.
The actress admits that despite the eye-watering wages on offer in Hollywood, the theater remains her passion.
She reflected: "The theater has always been my first love. I just love it. I love to be able to go out and just do a play."
Gemma confessed to relishing the "challenge" of performing in front of a live audience.
She said: "I like to be able to tell a whole story and have it be a little different every night. I love that challenge. I love to take on something really difficult and work at it. That's why I became an actor."