Orr's departure from Interpublic follows that of Ben Langdon in London last week. Langdon was head of Interpublic-owned McCann-Erickson Europe, where the worst of the accounting irregularties took place.
The scandal has forced Interpublic Group to restate $181.3m in earnings and led to the demotion of CEO John Dooner, who was knocked back to chief executive of McCann-Erickson WorldGroup.
Interpublic said that Orr had decided to leave the company, with his title and responsibilities to be assumed by Christopher Coughlin, chief operating officer, in August.
The news of his departure pushed Interpublic's shares up slightly to $13.25, still a long way adrift from its 52-week high of $25.36.
Frank Borelli, Interpublic's presiding director, said: "We understand and respect Sean's desire to move on to a new phase in his career. His efforts were significant in helping the company come through some of its recent difficulties."
He added: "Notably, Sean should be recognised for the role he played in identifying the accounting situation at McCann-Erickson in Europe, addressing it forcefully and beginning to put in place new, improved financial systems. We wish him well in whatever he chooses to do."
The scandal, which related to double booking of revenues at McCann-Erickson agencies in Europe, has caused massive ructions at parent company Interpublic. Sal LaGreca, chief financial officer of McCann-Erickson WorldGroup, left the company in the wake of the scandal.
Dooner was replaced as CEO of Interpublic in February this year by David Bell, who was chief executive officer at True North when it was bought in 2000. At the time, there was surprise that Orr was remaining in his job and speculation that he might not remain for much longer.
In a statement, Bell said: "Our initiatives to strengthen the balance sheet have been very successful and that key priority has been substantially accomplished. Sean has helped lead these efforts, for which we thank him. He has also graciously agreed to stay in his position until late August, so as to ensure a smooth transition of the corporate finance functions."
Bell said that this should allow Coughlin to remain focused on the "strategic priorities he is driving within Interpublic", namely: margins and operational reliability and accountability.
"Sean is a bright and capable executive and I know he will find interesting challenges in the future," Bell said.
Orr joined the company as chief financial officer in June 1999 from PepsiCo, where he was senior vice-president and controller. Before that, he was chief financial officer of PepsiCo subsidiary Frito Lay between 1994 and 1997.
He started his career with KPMG Peat Marwick in 1976 and was elected partner of the firm in 1986. He later joined the Reader's Digest Association in 1990 as vice-president and controller. He graduated from Boston College with a degree in mathematics.
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