WPP shares jumped 1.8% this morning and continued to rise, up 3.83%, or 18.75p, this afternoon to 508.75p.
Cordiant's depressed shares were similarly buoyed by fresh bid talk. Its shares were up 13.64%, or 0.75p, to 6.5p.
News of a possible WPP bid emerged at the weekend as pressure on Cordiant to secure a quick deal grew.
WPP had initially ruled out any bid, leaving French holding company Publicis Groupe as the only major advertising group to be seriously considering bidding for Cordiant.
A spokesman for WPP said: "With regards to Cordiant, we can only confirm that we are continuing to undertake due diligence."
Last week, shares in Cordiant tumbled by 20% after the group said it was considering an offer to buy the company that could value it below its current share price.
Shares closed at 5.5p on Friday, down more than 20% on the week after it said that it was talking to potential bidders about a sale, but warned "none of the proposals currently under consideration is likely to result in an offer at or near the current share price". Shares in the company were trading as low as 4.6p on May 22.
WPP is understood to have had discussions with Cordiant's bank UBS Warburg about a deal that could see it take on part of Cordiant's 拢250m debt.
However, it is understood that such a deal could face strong opposition from investors because it would give existing shareholders very little in return for their stake in Cordiant.
WPP, like Publicis, is interested in Cordiant's 141 Communications below-the-line business and its healthcare agency network Healthworld.
WPP is also said to be interested in Cordiant's Asia-Pacific business. Last week, Cordiant completed the sale of 70% of its Australian communications interests to venture capitalists and management.
The deal included its main agency George Patterson Bates. Cordiant now has a 30% minority interest in the business.
Whatever happens, Cordiant must make a deal quickly before the uncertainty forces any more clients to jump ship.
Cordiant was sent spinning and its share price plunging when Allied Domecq pulled its advertising. Since then, there has been speculation that more clients will follow.
Last week, there was speculation that B&Q was set to pull its advertising out of Bates. The account is major one for Bates, worth 拢32m. As well as Allied Domecq, Bates has already lost the Royal Mail and Woolworths accounts.
If a buyer is not found, Cordiant will continue with its disposal programme. It raised 拢24.6m from the sale of its Australian operation. Its public relations agency Financial Dynamics is on the verge of being sold to its management for around 拢25m, and the Germany-based Scholz & Friends ad agency is also up for sale.
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