The German competition authorities are opposed to plans by the country’s biggest electricity supplier, E.On, to buy a stake in the leading gas company Ruhrgas, the cartel office said on Monday.

E.On intended to take a stake in Ruhrgas as part of a complex deal with British oil giant BP, where they would reshuffle their respective oil and gas businesses.

BP would acquire a 51 per cent stake in E.On ‘s Veba Oel, which operates Aral, the leading petrol station chain in Germany.

And in return, E.On would receive a 51 per cent stake in Gelsenberg, the holding company for BP’s 25.5 per cent stake in Ruhrgas, one of Europe’s top three gas companies.

“In our estimation, the acquisition by E.On of a majority stake in Gelsenberg would lead to a market dominant position in both the gas and the electricity markets,” the cartel office said in a statement.

Office President Ulf Boege said: “Our warning is not a decision. But it is notification to the companies that, according to our analysis, the tie-up between E.On and Ruhrgas would cement Ruhrgas’s dominant market position at a time when the gas markets are beginning to be liberalised.

“That means that the opportunities for effective competition form other gas companies will be worse from the outset,” Boege continued.

“At the same time, E.On ‘s position on the power market will be further strengthened, which would have a negative effect on smaller rivals and therefore on the end-consumer as well.”