Barbour said in a statement on Friday that Charlie Williams, the governor’s chief of staff for the past four years, will serve as interim commissioner.
Phillips, who was not immediately available for comment about his future plans, has held the state’s top law enforcement post since May 2005. He is 59.
Paul Hurst, Barbour’s chief counsel for the past four years, will become chief of staff, replacing Williams.
The changes are effective immediately.