But all eyes were on UK advertising giant WPP, which has already tabled two offers for TNS. Analysts believe chances of an improved bid are good.

The combined TNS-GfK, which had revenues close to £2billion last year, will increase the pressure on market leader AC Nielsen in an industry whose importance has grown as companies seek more information on their clients and services.

TNS and GfK shareholders will each hold 50 per cent of the merged company’s shares. Its main listing and global headquarters will be in London.

At least £76million annual cost savings are expected by the end of the third year. The deal should be completed in the fourth quarter this year.

TNS chief executive David Lowden will retain that role in the merged group. “We are ideal partners. The new business will be a global leader in the market information industry,” he said.

“This merger will create substantial value for both sets of shareholders.” WPP declined to comment.