By William Boston And Todd Buell 

FRANKFURT--An era at one of Europe's biggest corporations ended dramatically Saturday when Ferdinand Piech, chairman of Volkswagen AG and grandson of the company's founder, unexpectedly resigned all duties after losing a rare public battle to oust the company's chief executive.

The supervisory board of Volkswagen, Europe's biggest automotive group by sales, said in a statement that Mr. Piech, who is 78 years old, tendered his resignation after the board's executive committee agreed that the "mutual trust that is needed for successful cooperation no longer exists."

That prompted Mr. Piech and his wife Ursula to resign all duties on the board and within the company.

Mr. Piech's resignation not only ends a battle for the leadership of the company known around the world for its popular cars from the iconic Beetle to the best-selling Golf and a stable of brands that include Audi, Porsche, Skoda, Bentley, Bugatti and Lamborghini.

Once given an award as automotive executive of the century, Mr. Piech's decision to quit also ends his 25-year reign at the top of Volkswagen, the company founded by his grandfather Ferdinand Porsche. Over the past quarter century Mr. Piech wielded enormous influence in the global automotive industry and steered Volkswagen to the top of the industry, challenging Toyota Motor Corp. and General Motors Co. for the industry's top spot.

The resignations are effective immediately and leave the family that controls 51% of Volkswagen's voting shares with just three representatives of the Porsche family on the board. It wasn't immediately clear what happens to the Piech seats on the board.

Berthold Huber, deputy board chairman and a representative of the IG Metall union, will take over as acting chairman until a new chairman is elected. The supervisory board is due to meet on May 4, a day before the annual shareholders meeting on May 5.

Write to William Boston at william.boston@wsj.com and Todd Buell at todd.buell@wsj.com

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