The Media group Aegis is to hold a shareholder meeting on November 22 to consider a fresh bid by the French financier Vincent Bolloré to win two seats on its board.
Aegis said it continued to recommend that shareholders vote against the election of Philippe Germond and Roger Hatchuel to its board, who were rejected by shareholders at a previous meeting in June.
Aegis, which owns the Carat and Vizeum agencies, has a market value of around £1.5bn.
Mr Bolloré, Aegis' biggest shareholder with a stake of 29%, is the chairman and top shareholder of the rival French advertising group Havas. If he crosses the 30% threshold he would have to launch a full takeover bid under UK rules.
"Any nominee put forward by Groupe Bolloré has an overriding conflict of interest that makes them inappropriate to act as a director of Aegis," Aegis said in a statement, saying it has no interest in merging with Havas.
"The board is strongly opposed to adding directors who may favour one particular shareholder group over and above the interests of shareholders as a whole."
In June, 94.1% of non-Groupe Bolloré shareholders voted against Mr Bolloré's candidates.
Earlier this week, the rival ad group Publicis said it considering acquiring another advertising company, fuelling speculation that Aegis could once again be in its sights.
In an interview with the Wall Street Journal Europe, Maurice Levy, the Publicis chairman and chief executive, said the company was looking at several strategies, including an acquisition, buying back shares, or paying a dividend to shareholders.
Last year, it was reported that Publicis had made an unsuccessful bid of 140p a share, or £1.56bn, for Aegis.
However, a renewed bid would require the agreement of Mr Bolloré.
There was friction between Mr Levy and Mr Bolloré recently when three senior Publicis executives defected to form a start-up ad agency backed by Mr Bolloré.
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