Mark Webber stunned Formula One when he said yesterday he was leaving the series after the season to race Porsche sports cars.
Webber said at the British Grand Prix he had signed a multi-year contract and will compete in Porsche's new LMP1 sports prototype at the Le Mans 24 Hours and in the world endurance championship next year.
He has struggled this season, failing to win a grand prix and is fifth in the drivers' championship, 63 points behind Red Bull teammate Sebastian Vettel. The German is on course for a fourth consecutive title.
Webber first raised doubts about his future with Red Bull after Vettel ignored team orders and overtook him for victory at the Malaysian Grand Prix in March.
Webber has long complained that Vettel, still only 25, is the Austrian-owned team's favourite and that position will only be enhanced for the remaining 12 races now that he has decided to leave.
Red Bull confirmed Webber was leaving and said they would make a decision on a replacement later in the season.
Among the favourites would be Lotus driver Kimi Raikkonen, who is a good friend of Vettel's.
That move would replace one of the sport's most outspoken drivers with the most taciturn and, at 33, second oldest after Webber, who will be 38 next year.
"I am sure Mark thought long and hard before making what has no doubt been a very difficult decision," Red Bull principal Christian Horner said.
"His achievements in Formula One are extensive and I am sure he will continue to push hard and build on that record until the end of the season.
"We support Mark's decision, he has been an excellent addition to the team since joining us in 2007 and we wish him all the best in the next stages of his career."
Since joining F1 in 2002, Webber has won nine races and had 36 podium places during a career that also includes stints with Williams and Minardi.
Webber's best season came in 2010 when he just lost a four-way battle for the title that was eventually won by Vettel.
The Australian started strong last season with victories at Monaco and Silverstone but then tailed off and only had two podiums the rest of the way.
With his age increasingly becoming an issue, there was talk that Webber needed a strong start in 2013 to retain his seat and give him any hope of winning a first title.
Porsche called Webber "one of the best and most successful Formula One pilots of our time".
"I learned to appreciate Mark's qualities when we were both involved in F1," said Fritz Enzinger, head of LMP1. "He is one of the best pilots I could imagine for our team. I'm absolutely delighted that we have such an experienced and fast regular driver onboard from 2014."
He has raced twice before at Le Mans. "I'm very much looking forward to this new challenge after my time in Formula One," Webber said. "Porsche will undoubtedly set very high goals. I can hardly wait to pilot one of the fastest sports cars in the world."