The French-based Publicis Groupe said the decision to pull out of negotiations with Aegis, which owns the Carat and Vizeum planning and buying shops, was made after a move to offer what would have been over £1.5bn for the group was said not to be in the best interest of shareholders.
The announcement came as so-called corporate raider Vincent Bolloré bolstered his share in the London-based Aegis by another 2.4% to a total of 17.4%.
Bolloré, who is also chairman of the Havas advertising network, owner of the Media Planning Group agency, said his continued interest and purchase of shares in Aegis will not lead to a takeover move.
In a statement, Publicis said: "Further to its statement of 22 September 2005, Publicis Groupe announces that it has decided that it is not in the best interests of its shareholders to make an offer for Aegis Group."
The fourth network involved in the ongoing saga, Sir Martin Sorrell's WPP, confirmed its interest in the group on Friday, but its "primary" interest was in the Synovate market research division of the Aegis empire.
Meanwhile, Aegis today paid out £10m for UK-based B2B planning and buying agency Just Media.
The agency counts the likes of Adobe, Borland, Cognos, Compuware, MessageLabs and Seagate among its roster of clients.
Robert Lerwill, chief executive of Aegis, said: "The acquisition of JML will complement and further strengthen Aegis Media's position in the UK business to business market.
"JML is a highly respected, professional B2B media agency with particular expertise in the technology sector.
"Combining JML with the market experience, tools and buying power of Carat Business will create many synergies and new opportunities that are expected to drive revenue growth and margin improvement, whilst continuing to deliver a market leading service to clients."
Just Media is headed by Sarah du Heaume.