Brown will replace Goran Larsson, who recently announced his intention to retire at the end of 2006.
Helen Kimber, the new- business director of Rainey Kelly Campbell Roalfe/Y&R London, will take on Brown's responsibilities as the new- business development director of Y&R, EMEA.
The promotions are intended to build on the agency's recent wins such as Volvic, Bacardi and Hitachi, and enhance service to existing clients. The new roles will report to Massimo Costa, the Y&R chairman of Europe, the Middle East and Africa.
Costa said: "Marcus has done an outstanding job in his three years at the helm of EMEA business development, for Wunderman as well as Y&R. He has orchestrated our regional wins and contributed greatly to many local market successes. Leadership of a local office is the logical next step for him and, as we change the focus of our Geneva operations, it presents an ideal opportunity for him."
He added: "In her two-and-a-half years with RKCR/Y&R, Helen has firmly established herself as one of the most successful new-business directors in the hugely competitive UK marketplace."