The 39 year old British star would play the role of evil Bellatrix Lestrange, a member of the Voldemort group.
A source said: "The producers have tried to keep details of the cast under wraps but they have always wanted someone beautiful and mystical to play Bellatrix and they reckon Liz can pull it off."
Before the release of Harry Potter And The Order Of The Pheonix, scheduled for June, 2007, fans can catch Harry Potter And The Goblet Of Fire opening in November.