Bob Benson, head of RL Benson Associates, a New Canaan, Connecticut, consultant to executive search firms, said: "It's still an old boys' network, and when it comes to top appointments, there's more focus on who knows whom than on doing a broad search" that includes outsiders as well as insiders.

Change is coming, though. German lawmakers earlier this year voted to require more than 100 of the largest listed companies to allocate 30 percent of vacant supervisory board positions to women starting next year.

Such changes are a way off at Volkswagen, where the Porsche and Piech families hold a majority of voting shares in the automaker and five seats on the supervisory board.

Two of the board family members are women, other women include Annika Falkengren, CEO of Sweden's Skandinaviska Enskilda Banken AB.

Mueller, whose contract as CEO goes until 2020, had run the maker of the 911 sports car since October 2010.

"My most urgent task is to win back trust of the Volkswagen Group－by leaving no stone unturned and with maximum transparency, as well as drawing the right conclusions from the current situation," he said in a statement.