Ricky Gervais has defended his new TV show Derek over concerns the sitcom mocks those with learning difficulties.

The British funnyman plays the title role in the series, which is billed as the story of "a simple, vulnerable man working in an old people's home."

The show is yet to be broadcast but Gervais has already been forced to address critics who claim the comedy makes light of the mentally disabled, insisting the character does not have a "specific and defined disability."

Gervais says, "Derek is a fictional character and is defined by his creator, me. If I say I don't mean him t...