Havas shares fell 13.1% to €5.65 (£3.50) in mid-afternoon trading, down significantly from yesterday's close of €6.50 (£4).
Havas' results have added weight to industry concerns about market uncertainty, something the French agency's CEO Alain de Pouzilhac warned of when he pulled out of the race to acquire Tempus.
Among the advertising fallers, Chime Communications, owner of Bell Pottinger PR, fell 5% to 114p and Incepta Group, parent of Citigate Dewe Rogerson, fell 4.8% to 30p. French agency Publicis slumped 6.6% to €16.25 (£10.09).
Tempus climbed 12% to 490p as news emerged that WPP Group had received 93.9% of acceptances for its takeover bid. However, that price is still far short of the 555p-a-share value of WPP's original bid for the media group and owner of CIA.
Meanwhile, WPP slid 6.4% as chairman Sir Martin Sorrell considers how to get himself out of the deal he muscled his way into.
Cordiant communications, however, joined Tempus on the way up, climbing 0.8% today to 65p.
As the FTSE 100 index lost 38.4 points to 4747.2 today, media stocks were forced to shoulder some blame for the fall.
United Business Media fell 8.3% to 346.5p and Pearson, owner of the FT, is down 5.9% to 660.5p. In France, media colossus Vivendi slid 6.5% to €46.34 (£28.70).
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