The former TBWA\London boss has already made the appointment of a new executive creative director his priority. But he has been rebuffed by his first choice, the M&C Saatchi senior creative Matt Eastwood.
As Grey's chief planning officer, Rossi was one of the management team that ran the agency before Lace's arrival. She was a key player in the agency's pitch for the global Electrolux account.
Rossi, who joined Grey six years ago, said: "My decision to leave has nothing to do with Garry's arrival. The fact is that I've been in the planning departments of large agencies for more than 20 years and it's time to do something different."
Lace, who is believed to want his own appointee as the planning chief, said: "Clare has done a great job here and we all wish her well."
Meanwhile, he has been forced to intensify his search for an executive creative director to replace Tim Mellors after Eastwood's decision to remain with M&C Saatchi.
Eastwood, an art director, had built a reputation as one of the best of Australia's new generation of creative directors. Lace is said to have hoped he might be a catalyst for a creative renaissance at Grey similar to the one sparked by Saatchi & Saatchi's Australian creative head, Dave Droga.
Eastwood was previously the creative director of the M&C Saatchi office in Melbourne. He is expected to win promotion in a forthcoming restructure of the London creative department.
The changes at M&C Saatchi are likely to mean a broader role for Simon Dicketts, the creative director, who wants to relinquish day-to-day control of the department
Moray MacLennan, M&C Saatchi's joint chief executive, said: "Matt just decided he didn't want to do the Grey job."
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