The 53 local authority shareholders in Dutch electricity provider Eneco have until next Tuesday to decide whether to sell or hang on to their shares but customers and staff are calling for caution.

Now three of the utility’s largest customers – Dutch Rail NS, telecoms provider KPN and supermarkets group Albert Heijn – have sent an open letter to the Eneco management board urging it to protect its sustainability philosophy.

The companies claim Eneco is in danger of losing this if the company comes into the hands of the highest bidder, an Eneco spokesman told the Financieele Dagblad on Friday.

Despite the fact that nearly half of Eneco’s electricity is generated by gas, the authors of the letter regard the utility as a ‘green precursor’ within the energy sector. The letter said Eneco has been working for years to concentrate on green sourcing which is courageous in a country so committed to fossil fuels.

In a reaction to the letter, Eneco said it was pleased its sustainability strategy is receiving support.

Shareholders

Latest estimates say shareholders representing 55% of the shares have voted to sell. But a majority of 75% is required for a new owner to have absolute control. The local authorities which have so far said they would not sell do not have the required 25% of the shares to block a sale.

A bourse listing is regarded as a safe compromise. An outright sale or an IPO could raise about €3bn.

Eight years ago, the two other main energy firms Nuon and Essent were also sold off, each for around €9bn. Nuon is now owned by Swedish state owned firm Vattenfall while Essent is the hands of German utilities group RWE.