July 23 (Bloomberg) -- Centrica Plc, Britain's biggest energy supplier, will take control of Belgian power generator Societe de Production d'Electricite after doubling its stake, thwarting a rival offer from Electricite de France SA.

Centrica exercised a pre-emption right to buy the 25.5 percent stake held by Gaz de France SA for 515 million euros ($813 million). With a customer base of 1.5 million energy accounts, SPE has a retail market share in Belgium of almost 20 percent. Electricite de France previously lost out on a bid to buy Distrigaz SA, Belgium's biggest natural-gas supplier.

``It's not at all surprising'' that Centrica would buy the stake, said Steven de Proost, a Brussels-based analyst at Dexia Bank NV. ``EDF has now missed out on Distrigaz and SPE which still leaves them short of natural gas and peakload assets.''

Gaz de France agreed to the sale to obtain European Commission approval for its long-planned merger with Suez SA. The Paris-based utility announced May 25 it was in exclusive talks with Electricite de France to sell its 50 percent stake in Segebel, which owns 51 percent of SPE. Centrica owns the other half of Segebel.

Centrica rose 6.75 pence, or 2.2 percent, to close at 310 pence in London.

`Logical Next Step'

``Today's transaction is a logical next step in building on our existing stake in SPE,'' Centrica's Chief Executive Officer Sam Laidlaw said today in a statement distributed by the Windsor, U.K.-based company.

Electricite de France spokeswoman Carole Trivi declined to comment on SPE or any other acquisition plans.

Electricite de France, the state-controlled utility which is the world's biggest operator of nuclear reactors, wants to increase its presence in Belgium and Spain. The company lost a bid to buy Distrigaz from Suez after Italy's Eni SpA agreed to pay 2.74 billion euros for a majority stake.

Centrica will also be liable for a deferred consideration of as much as 105 million euros payable later.

Gaz de France said on June 20 it agreed to sell the stake for 515 million euros, excluding the price of electricity drawing rights to be given to SPE by Suez's Electrabel SA unit, Belgium's largest power company.

SPE has 1,635 megawatts of power capacity, mostly at gas- fired plants. It has 4 percent stakes in the Doel and Tihange nuclear stations owned by Electrabel, as well as rights to power from Electricite de France's Chooz reactor in France.

To contact the reporter on this story: Ben Farey in London at bfarey@bloomberg.net

Last Updated: July 23, 2008 13:22 EDT