WPP is the single largest shareholder in WPP with a 22% holding and analysts are apparently concerned that WPP may enter into a bidding war to steal the company away from the French firm.
This morning, its shares were down 32p on yesterday's opening price of 687p, having fallen a further 10p on yesterday's close.
In June, WPP was believed to be pursuing a share-swap deal that would see it swap its stake in media-buying group Tempus for a stake in larger rival Aegis, which owns Carat.
Such a deal would have seen WPP swap its stake in Tempus for a 5% stake in Aegis, which is valued at £1.3bn compared with minnow Tempus's £332m prior to the Havas bid.
With Havas seen as a white knight bidder, Sir Martin Sorrell, CEO of WPP, might now make a move for Tempus.
However, relations between Ingram and Sir Martin are said to be poor, indicating that the WPP chief might simply take the money.
Shares in Tempus continued to climb yesterday, reaching 560p. It had already soared more than 50% earlier yesterday to 541p when the deal with Havas was first announced.
Yesterday Alain de Pouzilhac, chairman and CEO of Havas, said he had not spoken to WPP about his bid for Tempus.
WPP shares were put under further pressure as Publicis tied up its merger deal with Cordiant Communications to merge their jointly owned Zenith Media with the Publicis-owned Optimedia.
WPP is due to report is next set of results on August 20.