Taylor Nelson Sofres’ attempts to find more potential bidders have stalled because of a general reluctance to challenge WPP’s Sir Martin Sorrell, TNS’s chief executive told the FT.

TNS last night posted a document to shareholders explaining in detail why the board rejected WPP’s hostile cash-and-shares offer, worth 267p at Tuesday’s closing price of 497p. GfK, the German market research group, said last week that talks to raise funds for a rival bid were “progressing positively”.