Berlin: Germany has ordered surveillance to begin of British and US intelligence gathering on its soil for the first time since 1945, according to reports.
This means any US and British intelligence operations in Germany will be subject to the same counter-espionage measures as those used on Russia, China and Iran.
"We need to send a strong signal," a source close to the government of Chancellor Angela Merkel told the Suddeutsche Zeitung newspaper. The unprecedented move is a direct response to a series of spy scandals that have upset British and US relations with Germany in the past year.
Mrs Merkel's government gave the go-ahead to surveillance plans that emerged after two suspected double agents were found allegedly spying for the US inside the German security establishment earlier this month.
Relations were already strained after it was disclosed last year the US and Britain both use the roofs of their Berlin embassies as "listening posts" to monitor the German government, and that the US National Security Agency had eavesdropped on Ms Merkel's mobile phone calls. Germany has asked the CIA station chief in Berlin to leave the country over the double agent affair, an almost unheard of rebuke between allies.
The measures go still further and will bring to an end decades of co-operation that date back to the Cold War, when West German, British and US intelligence worked together against the Soviet Union.
From now on, the BND, Germany's equivalent of MI5, will extend its surveillance and counter-espionage operations to all foreign intelligence agencies operating on German soil.
But Ms Merkel's government has stopped short of a full retaliation, and has ruled out its own spying operations in the US.
There has been considerable irritation in Germany that it was excluded from the mutual no-spying agreement the US has with Britain, Canada, Australia and New Zealand under the Five Eyes alliance, and that Ms Merkel's requests for a similar agreement were rebuffed by the US.
It appears the new measures have been under consideration since it was revealed the NSA had spied on Ms Merkel's phone, but Germany had hesitated to implement them for fear of a confrontation with the US.
For months, Ms Merkel tried to downplay the spying affair, despite public anger in Germany as scandal after scandal erupted. It appears her government's patience finally ran out with the discovery of the two alleged double agents.
But there are indications that, while Germany is taking tough action in public, behind the scenes it is still trying to patch up relations with the US. In a sign that US President Barack Obama is taking German anger seriously, two senior US officials flew into Berlin for talks in recent days.
White House chief of staff Denis McDonough and Homeland Security adviser Lisa Monaco – an unusually high-ranking delegation – met the head of Ms Merkel's office and, according to a report in Frankfurter Allgemeine Zeitung, agreed to draw up policy guidelines for future intelligence co-operation.