UPDATE 1-TNS rejects improved $1.9 billion WPP offer

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LONDON, May 13 (Reuters) - British marketing research firm Taylor Nelson Sofres Plc (TNS.L: Quote, Profile, Research, Stock Buzz) rejected an improved 996 million pounds ($1.9 billion) takeover approach from WPP Group Plc (WPP.L: Quote, Profile, Research, Stock Buzz), saying it still undervalued the company.

TNS instead wants to press ahead with nil-premium merger talks with German market research firm GfK (GFKG.DE: Quote, Profile, Research, Stock Buzz) and said on Tuesday it expects to announce details shortly of the potential benefits of that proposed deal.

The rejected cash and share approach valued TNS at 241.8 pence per share, or 996 million pounds in total, based on the Thursday closing price of WPP, which includes the JWT and Ogilvy & Mather advertising agencies.

The bid was made up of 164p in cash and 0.1214 WPP shares for each TNS share, TNS said.

TNS earlier this month rejected a lower 950 million pounds, or 230 pence per share, offer from WPP.

"The board met today and had no hesitation in rejecting this revised proposal which substantially undervalues the company even on a standalone basis"," said TNS Chairman Donald Brydon in a statement.

"As previously announced, the board of TNS believes that a combination of TNS and GfK would deliver significant value to TNS's shareholders," TNS said.

"Significant progress has been made on the work to confirm the ... merger benefits and it is expected that a further announcement on these benefits and the key merger terms will be made shortly." (Reporting by Chris Wills; Editing by David Holmes) (chris.wills@thomsonreuters.com; 0044 (0)20 7542 5331; Reuters Messaging: chris.wills.reuters.com@reuters.net)) ($1=.5136 Pound)