Centrica, the owner of British Gas, wants to take control of Belgium's second-biggest electricity supplier, but will have to match a bid from EDF, the French state energy giant, to do so.

Sources in Paris suggested that EDF could offer a premium of between 5 and 10 per cent in an effort to knock Centrica out of the race.

The British group wants to take over SPE in a sale ordered by the European Commission as a condition for approving the €100 billion (£79 billion) merger between GdF, the French state gas group, and Suez, the Franco-Belgian utility. GdF has been told by the Commission to shed its 25.5 per cent stake in SPE, which it bought for €247million in 2005.

Centrica, which also owns 25.5 per cent of SPE, said that it planned to exercise its pre-emption rights on GdF's shares in a move to expand its operations in mainland Europe. However, Jean-François Cirelli, the GdF chairman, told analysts that he expected an offer from EDF this week.

A GdF spokesman said: “Centrica has to equal the bid if it is to acquire the stake.”

A source close to the negotiations denied that there was a plot between the two French state energy groups to keep Centrica out of the Belgian market. “GdF has a duty to its shareholders to sell to the highest bidder,” the source said.

SPE, which trades as Luminus, has 1.5million customers in Belgium and is also seen as a bridgehead into the French market. Local authorities in Belgium control 49 per cent of SPE.

The battle for the Belgian company comes with GdF and Suez planning to conclude their tie-up next month after 2 years of false starts and wrangles. The merger will create a European electricity and gas giant to rival EDF and E.ON, of Germany, with sales of €74 billion and a combined enterprise value of €105 billion. It will also give rise to the world's second-biggest water and waste management group, behind Veolia, another French group, when Suez spins off its environment division to form Suez Environment.

The merger will involve an exchange of 21 GdF shares for 22 Suez shares - effectively privatising the state gas supplier, but leaving the French State with 35 per cent of the merged company. Suez and GdF are to call shareholder meetings to vote on the plan on July 16 and plan to launch the merged group less than a week later.

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