- Steve McClellan

NEW YORK WPP Group has issued a formal offer to acquire research firm Taylor Nelson Sofres.

WPP posted the offer on its Web site Saturday, about the same time shareholders received the materials via standard mail, according to the London-based holding company. The offer values TNS at slightly more than $2.28 billion, based on the current rate of exchange.

German research firm GfK, a rival suitor for TNS, issued a statement urging the latter's shareholders not to accept WPP's bid "at this time," as it continues talks with potential partners to come up with a counterproposal.

WPP set an Aug. 29 deadline for TNS shareholders to accept the holding company's offer for the research firm, a cash and stock play.

GfK stressed in its statement that it is trying to arrange financing for an all-cash deal.

WPP's offer follows a hostile takeover bid on July 9 after three "friendly" but unsolicited offers were rejected by TNS' board.

Previously, TNS and GfK had approved a "merger of equals," but that agreement was terminated shortly after WPP revealed its takeover plan so that GfK could pursue a separate bid for the company.

GfK said talks with potential partners "are progressing positively. GfK therefore urges TNS shareholders to take no action in relation to WPP's offer for TNS at this time." But the firm also stated "no assurance can be given that an offer will be made."

After rejecting WPP's third proposal on July 2, TNS defined itself as "a unique company and has an attractive platform in this fast growing and dynamic sector and as such should command a commensurate premium valuation."

London-based TNS also accused WPP at the time of making undervalued bids "and [generating] considerable press commentary and innuendo...purely to frustrate the merger of GfK and TNS."

If it succeeds in acquiring TNS, WPP would merge the company with its Kantar market research arm. The resulting combined company would become the second-largest global insight, information and consultancy group behind Adweek parent the Nielsen Co.

This story updates an earlier item with the news that WPP has posted it latest offer.