Unilever is a significant client of Carat, for which it handles media for the Wall's ice cream range, as well as ready meals and frozen fish.
Strauss, whose full title is chairman of the North America Committee and president and CEO of Unilever US, was appointed to head the US operations of Unilever in August 2000. Prior to this, he was part of Unilever's home and personal care division in North America.
His career at Unilever began in 1986 when he joined as president and chief executive officer of Ragu Foods and, in 1992, he became chief executive of Lever Brothers Company, New York.
He has a background in marketing and worked for a period in the UK for the bra company Playtex.
Lord Sharman, chairman of Aegis, said: "I am delighted that Charles has decided to join the board. He brings considerable international experience to Aegis and we look forward to his contribution."
According to the company website, Strauss, 60, is interested in classical music and American and English decorative and visual arts of the 20th century, and enjoys a game of tennis.
Other non-executive board members include: former chairman and chief executive of Mattel in the USA, John Amerman; former Rank Xerox chief executive, Bernard Fournier; Leslie Van De Walle, president of Shell Europe Oil Products; and Robert Lerwill, executive director of finance and CEO of regional business at Cable & Wireless.
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