- Steve McClellan

NEW YORK WPP Group today extended for a fourth time the deadline for acceptance of its nearly $2.2 billion offer to acquire research firm Taylor Nelson Sofres.

Despite calls by TNS management for shareholders to reject WPP's cash and stock bid as too low, owners of nearly 61 percent of the company's outstanding shares have agreed to be bought out -- up from 34 percent a week ago, WPP said.

The new deadline is Oct. 8. Terms remain unchanged, and WPP has consistently said it would not sweeten its offer. A possible exception would be if a rival bidder emerged, but none has since GfK exited the process in August.

One wrinkle in this week's developments: London-based investment-fund manager Cedar Rock Capital has increased its ownership stake in TNS to just over 10 percent. If Cedar Rock maintains that position, WPP won't be able to force minor shareholders to sell, because it would be required to hold 90 percent of the shares to do so under U.K. laws. Cedar Rock has supported TNS' position that WPP was paying too low a price for the company.

TNS CEO Donald Brydon reiterated that stand earlier this week. In a statement, Brydon said: "It's been pretty clear to us all along that this offer doesn't properly value the company. There is still a significant shareholding that agrees with us."

The upshot is that WPP, should it prevail, which seems increasingly likely, could end up with a thorny and vocal minority shareholder in Cedar Rock.

TNS has said the holding company's proposal is too low given the research firm’s strong financial performance in the first half of 2008 and its "leadership" position in its market sector. WPP has said it "believes the offer provides a substantial premium for TNS share owners with both cash certainty and potential equity upside" from WPP shares.