It comes as a serious blow for troubled Interpublic Group, which had assured investors that it was confident it could keep hold of the work.
No other agencies were involved in the review for the business of the car giant, which is the second-biggest advertiser in the US after Procter & Gamble.
The account was won by the Chicago office of Starcom MediaVest, which is where the media network is headquartered.
Michael Roth, chairman and chief executive of Interpublic, had cited the company's success in repitching for the European GM account, which is held by Initiative in the UK and Universal McCann in Germany.
The news of the GM review came in March, only days after Interpublic revealed it would not be filing its annual results for 2004 on time, and that it had uncovered $145m in overstated revenues, relating to acquisitions made between 1996 and 2001.
Interpublic ran the GM account through General Motors Mediaworks, its dedicated buying agency for the car manufacturer.
General Motors has troubles of its own, recently reporting a $1.1bn loss for the first quarter. However, its shares have been on the up since billionaire investor Kirk Kerkorian offered to buy 28m shares in the company for around $870m.
The carmaker is due to confirm the outcome of the review later today.
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