Advertising company WPP is encouraging shareholders in Taylor Nelson Sofres (TNS) to put pressure on the board of the company to engage in takeover talks with WPP. The news comes after TNS said it rejected a £950 million (230 pence per share) offer from WPP on 4 May.

Sir Martin Sorrell, Chief Executive of WPP, said, We are surprised and disappointed that the Board of TNS has rejected our offer proposal within 24 hours of receipt.

We are puzzled that our attempts to engage with TNS management on a friendly basis have been hindered and resisted. We are also disappointed that TNS has not indicated that it would be willing to provide us with the same information which it has given to GfK as part of their 'nil premium merger' discussions, despite the fact that we would be entitled to such information were the UK Takeover Code to apply.

While we continue to review our position, we encourage TNS shareholders to urge their Board to engage with us rather than simply persisting on an exclusive basis with a 'nil premium merger' arrangement with GfK.

WPP made it clear that there was no certainty that any new offer for TNS would be made, and said that a further announcement would be made, if and when appropriate.