The European Union antitrust authorities said Wednesday they are opening an in-depth investigation to assess whether Germany is distorting competition by exempting large electricity consumers from paying network charges.

"If this turns out to be the case the Commission will further examine whether the exemption is likely to unduly distort competition in the EU or whether it can be justified," the European Commission, which has antitrust powers in the EU, said in a statement. "Opening an in-depth investigation does not prejudge its outcome. It allows Germany and third parties to comment on the measure under review," it explained.

According to German law, since 2011 large electricity consumers are exempt from paying network charges for an amount estimated roughly at 300 million euros ($390 million). A special levy on final electricity consumers makes up for the money discounted, an issue that has prompted many consumers associations, energy companies and citizens to complain to the commission.

"The Commission's preliminary view is that the...surcharge may constitute a State resource and that the exemption seems to give the beneficiaries a selective advantage compared to their competitors in other member states," the commission said.