The Ifop deal, which is being backdated to January, will make GfK the leading supplier of sales data for the entertainment industry in France, the firm said.

Ifop Music is responsible for producing weekly charts based on music sales and downloads for French music association Syndicat National de l’Édition Phonographique. The firm will continue to trade under its own name. GfK Retail and Technology already offers sales tracking services for books, DVDs and computer games.

GfK has also bought a 25% stake in Cypriot audience measurement agency Watch Media. The deal includes a purchase option for a majority stake and takeover.

Watch Media operates a panel of 7,200 people and measures the reach of 32 radio stations, 27 TV stations and 57 printed titles using Mediawatch, a wristwatch-like device supplied by GfK Telecontrol.

• In other news today, GfK said it had increased the size of its household panel in Germany from 20,000 to 30,000 homes, creating what the firm claims is the largest sample in Europe – a title previously held by TNS’s UK panel. GfK is also increasing the size of its single-source panel, which measures both purchases and media consumption, from 7,000 homes to 15,000.