According to measurements by a government desktop app, the fixed-line Internet in many households in Germany is significantly worse than contractually agreed.
As the Federal Network Agency informed the German Press Agency on request, consumers have received almost 15,000 so-called measurement protocols as part of a reduction right that has been in effect since December.
A reduction claim was "almost exclusively" determined - the service had such major defects that the consumer was entitled to a lower payment.
The logs do not say how high the reduction is - consumers should clarify this with their providers.
Netzagentur boss Klaus Müller said they were pleased that the measuring tool "breitbandmessung.de" was being well received.
"We help thousands of consumers to prove their provider is underperforming."
Internet tariffs contain a product information sheet in which the provider specifies the maximum, minimum and data rates normally available.
There must be no "significant, continuous or regularly recurring deviation" from these requirements, as a law states.
However, the results of the fixed network measurements now show deficits from which legal claims can be derived.
There had already been similar measurements in the past few years, they had also shown a discrepancy between the contractual specifications and reality in the fixed network.
A legal claim did not result from the older measurements - this has only been the case since mid-December.