AOL Time Warner's German unit has filed a complaint against Europe's largest Internet service provider T-Online International with the German telecoms and post regulator RegTP.
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"The complaint includes the point that T-Online sets and offers retail prices below actual costs", an AOL spokeswoman said.
AOL Germany is the second largest German internet provider after T-Online. It maintains that its competitor is offering Internet access at unfairly low prices. Deutsche Telekom, which owns an 81.7 percent stake in T-Online, is apparently subsidising this so that its own brand can gain market share.
The regulator said it was following leads on potentially anti-competitive Internet access pricing by T-Online.
The difference between retail prices charged by T-Online and wholesale prices for Internet connections charged by Telekom had aroused suspicion that Telekom was trying to secure a competitive advantage against its rivals, RegTP has said.
RegTP also said it did not consider Telekom's Internet provider a separate company. T-Online remains one of Germany's more expensive providers. However, rivals are accusing it of exploiting its size and its direct relationship with Deutsche Telekom to force other providers to slash costs in order to be able to compete.