The French holding company ran into trouble last month when it hired a 30-year GM veteran, Kurt Ritter, to run the US Toyota Motor account, which is held by Publicis-owned agency Saatchi & Saatchi.
GM was unhappy that one of its executives had been poached by one of its largest advertising partner to work on the business of a rival.
GM publicly criticised Publicis in an article in the US magazine Ad Age. In the article, CJ Fraleigh, the executive director for corporate marketing and advertising at GM, said the hiring of Ritter by Saatchi & Saatchi was "unacceptable and inappropriate".
He also indicated that GM had made its displeasure clear and was considering what steps to take.
The carmaker put pressure on Publicis to move Ritter and the advertising firm has complied, with Ritter making a sudden departure from Saatchis. It is understood that he will now work on a consultancy basis.
It is unusual for a client to so publicly demand changes and highlights the problems agencies face when it comes to client conflict. Despite the account being held by entirely different parts of Publicis global operation, the managing of such relationships is still fraught with difficulty.
Publicis handles over $350m (£210m) of GM advertising, spread across its Leo Burnett agency and its newly formed Chemistri operation, which was formerly D'Arcy Detroit and is now dedicated solely to serving the brands of GM.
Chemistri works on marques including Cadillac and Pontiac, as well as GM Service & Parts operations and several global GM operations.
While Chemistri operates as a standalone agency, it is linked with Leo Burnett Worldwide. GM spent $2.5bn on its advertising during 2002, a rise of 12.5% on 2001.
Ritter was hired by Publicis in April to oversee the Toyota Motor Sales USA account at the Saatchi & Saatchi operation in Torrance, California, where he was named chief executive. The account is the office's biggest.
He joined from GM's headquarters in Detroit, where he was most recently general manager for the Buick and Pontiac divisions of the US car giant and had previously worked in various senior marketing and other executive roles at various GM units over a 30-year period.
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