In 2012, Pope Benedict XVI congratulates Ferdinand Piech (r) with his 75th birthday. Winterkorn also was present (Photo: VW)

Contrary to expectations, Volkswagen CEO Martin Winterkorn may not move up to head the company's supervisory board when he retires from his operational role at the end of 2016. Germany's Spiegel magazine says that Winterkorn and VW patriarch Ferdinand Piech have had growing disagreements over the business development of Europe's largest automotive group.

"I'm at a distance to Winterkorn," Piech is quoted as saying.

According to the Spiegel report, Hans Michel Piech another Porsche-Piech family member who sits on VW's supervisory board, is unhappy that VW's US business continues to underperform, the VW brand's operating margins are seen as too low and the carmaker, despite years of discussions, hasn't yet launched a new low-cost brand. Ferdinand Piech already expressed unhappiness with VW's performance a year ago. When asked in March, 2014, whether he thought the group was heading in the right direction, his answer was: "Not really."

The Porsche and Piech families together control 53.1 percent of Volkswagen Group shares. Winterkorn has for decades been a close ally of Ferdinand Piech.

The supervisory board chairman is quoted as saying that his wife Ursula, who also sits on the supervisory board, won't become chairman when he steps down. The council won't be headed by a family member, Piech said, adding that a decision will only be made in 2017, "shortly before I step down."

According to Der Spiegel, candidates to succeed both Winterkorn and Piech are available within the company. Several top executives have been touted as possible future CEOs. They include Audi boss Rupert Stadler, VW Commercial Vehicles head Andreas Renschler and soon-to-be Volkswagen brand CEO Herbert Diess. Rentschler joined VW from Daimler and Diess from BMW. Diess will assume his new responsibilities July 1.

Because Winterkorn was seen as the clear successor for the supervisory board chairmanship, there have been few if any suggestions for alternatives.