The number of those who have accepted the offer trebled from 11% on September 12 in the space of a fortnight that was marked by further deterioration in the economic outlook and by the .
WPP, led by chief executive Sir Martin Sorrell, has now given TNS shareholders who have not yet accepted the deal until this Friday to change their minds.
The offer is unchanged, consisting of 173p in cash and 0.1889 of a new WPP share. Based on WPP's share price at the stockmarket's close on Friday of 473.75p, this values TNS at £1.15bn.
Following the publication of the number of acceptances on Friday, TNS put out a statement again urging its shareholders to reject the offer.
Its board believes the offer undervalues the company and fails to take into account factors such as the business's current performance, its market-leading position; its growth strategy and investment in a global and digital offering.
TNS also argues that previous acquisitions in the sector have valued target companies above WPP's valuation of TNS.