13 Films handles international sales on Public Affairs and introduced the project to buyers in Cannes last month.
Birch will join previously announced Adrian Grenier and Mimi Rogers
Eric Bross directs Public Affairs from a screenplay by Tom Cudworth about a campaign aide who must fight for his life after he sleeps with the wife of a presidential candidate.
School Pictures’ Stephen Israel and George Voskericyan of American Film Productions serve as producers.
Birch took a break from acting after she broke out in American Beauty and earned a Golden Globe nomination for Ghost World.
She is shooting Above Suspicion and recently wrapped The Etruscan Smile.