The agency is poised to appoint TBWA\Paris' chairman and chief executive Arthur Sadoun (the former strategic planning director of TBWA\Worldwide) and the strategy director Valerie Henaff.
It is understood they will take over the reins at Publicis Conseil following Lambert's decision to join Frederic Raillard and Farid Mokart, the founders of the Publicis-owned boutique agency, Marcel, at a new start-up.
The trio's decision to quit Publicis Groupe for a new agency backed by the Havas chairman, Vincent Bollore, caused a furore within the French advertising industry.
Marcel had been a huge success for Maurice Levy, the chairman of Publicis Groupe, having won the fiercely fought contest for the France Telecom account. He is understood to have been furious at the defection of Mokart, Raillard and Lambert.