The French advertising group, chaired by Vincent Bollore, concluded the agreement this week with Scher Lafarge founders Gilbert Scher and Christophe Lafarge, who used to manage the Citroen account while at Havas between 1992 and 1998.
Havas says the deal has been made to "contribute to the development of Citroen", a historic account of the group in France and internationally.
French newspaper Le Monde had previously reported that Citroen was unhappy with the handling of its account by Havas and hinted that it would like to work with the Scher Lafarge founders again.
The deal was proposed by Jacques Seguela, vice-president of Havas, and approved by the executive committee of Havas.
According to Havas, Scher, Lafage, and Benoit Devarrieux and Jean-Pierre Villaret, directors of Havas unit DevarrieuxViallaret, have expressed a common interest in merging the two agencies.
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This article was first published on brandrepublic.com