Between 20,000 and 30,000 German households received legal warnings for having viewed copyrighted pornographic films via the streaming website RedTube.com, The Guardian reported.

Initially, it had been assumed that a court error had led to the sending of the letters, which ask for the payment of a €250 fine to the Swiss media agent that claims to hold copyright for the films, including Amanda's Secret, Miriam's Adventure and Glamour Show Girls. But now the legal firm behind the warnings says it plans to look into more infringements on porn streaming sites in the coming year. "Redtube was more like a test balloon," Thomas Urmann of U+C told German media.

Were the Bavarian law firm to succeed, it would set a worldwide precedent. In the past, streaming sites have been able to circumvent copyright law, as no copy of the original work is created. But U+C, which specialises in file-sharing cases, argue that viewing clips on streaming sites can constitute a proliferation of copyrighted material since a tiny copy of the file is created in the memory of their computer.

Urmann said the letter had elicited responses from hundreds of internet user households, some of them from irate wives and partners. "Most of the conversations, however, have been very factual and businesslike."

RedTube's Alex Taylor released a statement saying: "RedTube stands by its firm opinion that these letters are completely unfounded and that they violate the rights of those who received it in a very serious manner," describing the court's actions as blackmail and a violation of privacy, The Guardian reports.