Germany's leading commercial broadcaster RTL is making its biggest ever investment by acquiring a 49.9% stake in sister channel Vox, according to RTL chief executive Gerhard Zieler in an interview with German daily Sueddeutsche Zeitung.

The stake is currently owned by RTL parent company, Luxembourg-based CLT-UFA, which bought News Corp's 49.9% interest in Vox shortly before Christmas for a reported DM650m. Zeiler stated that Vox will remain independent under the management of Anke Schaeferkordt and would concentrate on "upmarket", "sophisticated" programming as well as featuring repeats of RTL formats.

In addition, RTL will now have access to attractive programming, including Titanic, which Vox acquired from Rupert Murdoch's 20th Century Fox as part of an output deal. The move is part of Bertelsmann's plans to create a "family" of channels to compete with the rival "family" of broadcasters being lined up by the KirchGroup which includes Sat1, ProSieben, Kabel 1, DSF and N24.

"Our four channels (RTL, RTL2, Super RTL and Vox) will hopefully work together even more,' Zeiler said, although he stressed there are no plans for RTL to take direct stakes in RTL2 or Super RTL.