Luxembourg-based RTL Group and Spain's Grupo Planeta have reached an agreement which could see both companies increasing their stakes in Spanish free-to-air broadcaster Antena 3.

Following the IPO of Antena 3 planned before year-end, RTL Group and Grupo Planeta could up their respective 17.2% and 25.1% shares in the channel, the companies said Monday.

RTL Group will also retain its two existing seats on Antena 3's board of directors, to be occupied by finance director Thomas Rabe and Nicolas de Tavernost, CEO of RTL Group's part-owned French subsidiary M6.