A large majority of the company's 53 municipal shareholders voted in October to privatise Eneco, while CEO Jeroen de Haas and works council chairman Willem Hofman had lobbied against it and pressed for conditions including preservation of its profile as a renewables-focused business.

The company said on Monday that De Haas, CEO since 2007, will leave on Sept. 1. Eneco said its supervisory board reached the decision "in close consultation" with De Haas but declined to clarify the reasons for his departure.

Hours later the works council issued a statement signed by Hofman, saying it will ask the Amsterdam Enterprise Chamber to launch an inquiry into De Haas's departure and other recent actions of the supervisory board.

Eneco spokesman Edwin van de Haar read a statement from the company's supervisory board, saying that it is preparing for the works council's actions.

After months of feuding, shareholders and Eneco's boards had agreed in February that the company would be sold, paving the way for privatisation in the coming months.

Details of the sale process have not yet been made public, but sources familiar with the matter told Reuters that the company was seeking a trade sale as its preferred option, with an initial public offering as second choice.

Despite the agreement with shareholders, Eneco's works council said it still fears a sale to a party that would harm its sustainable profile.

"Basically it comes down to the question whether it would be conceivable for Eneco to be bought by a company like (Royal Dutch) Shell ," spokesman Jan Driessen said.

Eneco, estimated to be worth about 4 billion euros (3.46 billion pounds), is heavily invested in sustainable energy projects and could appeal to companies that want to increase exposure to renewables.

Potential bidders include Shell, Total, Enel, Engie, Verbund, Orsted and Fortum.

Eneco spokesman Van de Haar said that the departure of De Haas is not expected to have any effect on the sale of the company.

(Reporting by Bart Meijer and Toby Sterling Editing by Mark Potter and David Goodman)

By Bart H. Meijer