Investigators from the European Commission raided the offices of Électricité de France (EDF) yesterday seeking evidence of price-fixing in the French electricity market.

Commission officials were joined by inspectors from the French Competition Authority in a raid on the utility's headquarters in Paris.

The Commission said that it suspected that EDF was engaged in activity that abused its dominant position in the market. “The suspected illegal conduct may include actions to raise prices on the French wholesale electricity market,” it said.

EDF said: “European Commission investigations are under way and the company is fully co-operating.”

The Commission is already engaged in an extensive inquiry into the European energy market. That investigation into the gas and power sectors was launched in 2007. The Commission believes that big players in those sectors are dragging their heels in the implementation of European Union directives requiring that dominant companies open up their markets to rivals.

The Commission said that its inquiry had given it “an in-depth understanding of the functioning, and in some respects, the malfunctioning of the energy sector”.

Meanwhile, fresh questions have emerged over Centrica's £3.1 billion plan to buy a stake in Britain's nuclear industry, amid growing signs that talks are set to continue into the spring.

Despite past pledges by both sides that a deal would be sealed early this year for Centrica to buy a 25 per cent stake in British Energy from EDF, the owner of the UK nuclear generator, the two companies have been unable to reach agreement. Sources said that it looked increasingly unlikely that an agreement would be announced before a deadline set by EDF of the end of this month.

Some investors in Centrica, the owner of British Gas, have been sceptical about the logic of the deal. It was struck in September, just before wholesale electricity and share prices plunged, a development that has prompted some to suggest that the funds would be better used elsewhere.

The price of electricity fell to £34.75 per megawatt hour yesterday, its lowest in a year. It was at £80 when Centrica announced plans to buy the 25 per cent stake in September.

A spokesman for Centrica, which said that it remained committed to the deal, declined to comment on the talks.

Sam Laidlaw, Centrica's chief executive, raised the prospect last month that the plan could be abandoned if it did not deliver value for shareholders.

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