European Commission President Jean-Claude Juncker said the process to appoint his successor, Germany's Ursula von der Leyen, was not transparent and marked an unwelcome break with the practice of choosing parties' lead candidates.

"The process was not very transparent," Juncker told, replying to a question about how EU leaders this week selected the next president of the EU executive. The nominee requires European Parliament approval.

He added that his appointment five years ago was transparent as he was chosen by leaders after having campaigned in European elections.