Recent revelations about the NSA’s broad surveillance of German phone and Internet communications have fueled major concerns in the country, as Federal Prosecutors say they are preparing criminal charges against US and British spies involved.

Hessian prosecutors were the first to receive complaints about the matter, but that is likely to grow precipitously after German media outlets reported the US surveillance has collected more than half a billion phone calls and emails per month in Germany alone.

Though broad internal surveillance is also an issue in the US, the NSA’s policies don’t make spying on Germans illegal as such. The US lists Canada, Britain, Australia and New Zealand as “second party” nations exempt from surveillance, but considers Germany fair game. The program also explicitly targeted European Union diplomats.

Justice Minister Sabine Leutheusser-Schnarrenberger said the US policy was “beyond comprehension,” and said that such “Cold War” methods were unacceptable toward allies. Officials are urging the EU to take direct action to stop the surveillance.