-By Steve McClellan

NEW YORK In an abrupt reversal Monday, the management of London-based market research firm TNS waved the white flag and recommended that shareholders who hadn't already done so accept the WPP offer to buy them out.

Word of the TNS board's capitulation comes just three days after WPP reported that shareholders accounting for nearly two-thirds of TNS shares had agreed to accept the WPP offer, which values TNS at nearly $2.2 billion.

Up to now, the TNS board has steadfastly rejected the WPP offer as one that undervalues the company.

Even the board's statement today said that that continues to be the case, but that the remaining minority of shareholders who didn't accept the offer faced the likely reality of owning shares in a company that will soon be delisted from publicly traded exchanges. Under U.K. regulations, WPP could delist TNS once it acquires 75 percent of the outstanding shares.

Therefore, TNS management said in a statement, "The board, which has been so advised by Deutsche Bank [and others], now recommends that shareholders accept the WPP offer, as the directors intend to do in respect of their own beneficial holdings."

Last Friday, WPP extended its offer to buy TNS shares until Oct. 8.