Sky will find it a "challenge" to retain the rights to televise all of the lucrative English Premier League soccer matches in the next round of auctions for the games, the head of rival BT Sport told CNBC.

BT Sport shook up the live sport broadcasting market, previously dominated by Sky Sports, in 2012 when it launched a £738 million ($1.2 billion) bid to show 38 Premier League games per season between 2013 and 2016.