As reported in Motorsport.com and also BBC Sport:
"Jun.27 (GMM) Mark Webber is retiring from formula one at the end of the year in order to drive for Porsche's new Le Mans prototype programme in 2014 and beyond.
The popular and outspoken 36-year-old Australian has driven for Red Bull since 2007, and has more than 200 grands prix under his belt, including nine wins.
"I'm very much looking forward to this new challenge," Webber said in a statement.
2007 world champion Kimi Raikkonen is the favourite to replace Webber at Red Bull."