The move could ratchet up already worried trans-Atlantic tensions.
Germany has summoned the US ambassador over a ‘breach in trust’, following reports that the US intelligence agencies spied EU offices.
The US National Security Agency (NSA) is alleged to have tapped about half a billion phone calls, emails or mobile phone text messages in Germany per month, making it the most targeted among states in the European Union.
The latest claims over the extent of US spying on Germany are projected to ratchet up already worried trans-Atlantic tensions.
According to internal NSA document, cited by German news magazine Der Spiegel, the US categorised Germany as a ‘third-class’ partner and the surveillance was stronger than in any other EU country, same as in China, Iraq or Saudi-Arabia.
"We can attack the signals of most foreign third-class partners, and we do it too," the NSA document said.
The NSA document also revealed that the agency had examined about 20 million German phone connections and 10 million Internet data sets on an average day, increasing to 60 million phone connections on busy days.
The metadata that shows details about when a communication was made and with whom has been saved at the agency’s headquarters, the report said.
Reports also reveal that the NSA targeted EU offices in Brussels and the US. Conversely, Germany sought an instant explanation over the report and alleged that the US intelligence activity was indicative of the Cold War.
Earlier, the US PRISM programme leaker, Edward Snowden, accused the NSA of hacking China’s three state-run telecom companies to snoop on SMS data from the Chinese data carriers.