Audience measurement firm Taylor Nelson Sofres has confirmed its merger with German rival GfK in a probable attempt to stave off a third acquisition bid from Sir Martin Sorrell’s WPP. The pair agreed a nil-premium 50-50 merger that would create the world’s second largest market research outfit after Nielsen and would be valued at just under £2 billion. But most expect Sorrell to come back with another offer, following its 241.5p bid . TNS CEO David Lowden (via Times Online) said WPP would “have to make a proposal at a premium to the current share price”. TNS rubbished WPP’s first £948 million valuation as “derisory”. It last bid 241.5p (£996 million) per share though one analyst quoted by The Times reckons 285p would be fairer but Sorrell has clout enough for 300p.