The hit TV show is set to make the move to the big screen next year and will see Agnes take on a syndicate who want to build a shopping centre where her stall is.
She is defended in court by a Tourette’s Syndrome suffering barrister - the role O’Carroll wants Bonneville to play.
He told The Sun: “This barrister hasn’t represented anyone for five years because when he is under pressure he develops Tourette’s. I’m hoping to get Hugh Bonneville for the part - I wrote it with him in mind and couldn’t stop laughing - I think he’d be brilliant.”
Filming for the movie, which will have a budget of around €4.5m, is scheduled to begin towards the end of the summer, with the aim of a 2014 release.