Previously, Cotter was the managing director of The Facilities Group, Saatchis' production operation. He will work with James Hall, who has taken the position of group chairman in addition to his role as the chief executive of the Saatchis ad agency.
The low-profile Cotter is a surprise appointment but his financial background may prove valuable as Publicis attempts to steer Saatchis through the recession.
Saatchis has made its mark creatively over the past couple of years, recently winning Agency of the Year at the Cannes International Advertising Festival. However, the agency has suffered during the advertising downturn and over the past year it has lost its Army and Lloyds TSB accounts. Its Sony and Telewest accounts are both under review at present.
Cotter, who worked as the agency's finance director during the days of Maurice and Charles Saatchi, will be replaced by Sue Richardson as the managing director of TFG. Mike Parker's position as the managing director of Team Saatchi is unaffected by the restructure.
Hall, who as the group chairman will now oversee Saatchis, TFG and Team Saatchi, believes that the move will enable the three divisions to develop closer relations.
Hall said: "This will enable us to drive the group in a synergistic way, ensuring the separate divisions don't compete with each other."