Roger Michell will direct the film, which centers on a couple who take a trip to Paris to revitalize their marriage. Jeff Goldblum, who recently starred in Broadway's Seminar and has been seen on the Fox hit series "Glee," is also in negotiations to appear in the film.
Duncan won the Tony Award in 2002 for her performance in Private Lives and was nominated for Les Liaisons Dangereuses. She has also been seen on Broadway in A Midsummer Night's Dream.
Broadbent, known for his film roles in "Iris," "Moulin Rouge!" and "Bridget Jones' Diary," has been seen in the West End productions of The Pillowman and Theatre of Blood, among others.
Film 4 and Kevin Loader will produce "Le Weekend."