In a statement the company said his departure was "the result of differing views regarding the long-term direction of the business between Mr. Hartmann and the majority shareholder, GfK Verein."

Arno Mahlert, chairman of the supervisory board, also resigned.

Hartmann (pictured) has been CEO since 2011 and oversaw a reorganisation and move into digital. He had previously spent more than 20 years at IBM.

Until the end of the year his responsibilities will transfer to the management board and Dr. Gerhard Hausruckinger will take the role of interim speaker for the management board as well as carrying on his current role leading the Consumer Choices sector.

The news of Hartmann’s departure comes as GfK posted lower sales and income for the first half of 2016.

Sales in the first half of 2016 were down 1.5%; adjusted operating income was down by €12.3 million to € 58.9m on the same period the previous year. Although there was stronger organic growth in the Consumer Choices business it was offset by a fall in sales in the Consumer Experiences sector.

Hartmann said: “The second quarter of this year was disappointing. We had to set up provisions as a result of delays with growth initiatives in the Consumer Choices sector. Our focus now is on resolving start-up problems with these projects and increasing the external order intake in the Consumer Experiences sector. The additional cost-cutting measures and adjustments to resources implemented will contribute positively in the second half of the year. On the positive side, we had a strong cash flow.”

The Consumer Experiences sector reported a sales decrease of 7.8% in organic terms for the first half of the year, following a weak order intake for traditional ad hoc research.

The Consumer Choices sector continued to grow although the company said delays in television audience measurement contracts and other growth initiatives as well as the results of the now sold Animal and Crop Health business significantly impacted the sector’s margin.

In Media Measurement, start-up problems with new contracts affected results, especially the TV audience research contract in Brazil.

In terms of regional business, Latin America and Central Eastern Europe/META reported robust organic growth although there were negative currency effects. In the mature markets of Northern Europe, Southern and Western Europe as well as North America it was a downward trend.