Manfred D, former head of cabinet to ex-intelligence chief August Hanning, was taken into custody on charges of aiding and abetting treason. He is accused of obtaining classified BND documents and passing them to Hanning in exchange for payment since 2010.
Following the arrest of former BND chief August Hanning on Tuesday in Germany's biggest espionage scandal, his long-standing confidant and former head of cabinet Manfred D has now also been taken into custody.
Federal prosecutors accuse both men of having used state secrets over many years to support private consulting activities and foreign interests, a crime that constitutes treason.
Manfred D, 64, has been charged with aiding and abetting and remains in pre-trial detention, while Hanning is being brought before an investigating judge, according to reports.
Manfred D previously served as head of cabinet to former intelligence chief August Hanning. The two men have known each other since the late 1990s and worked closely together for many years at the BND and later at the Interior Ministry.
Prosecutors say Manfred D obtained classified documents from the intelligence service and passed them on to his former boss Hanning, allegedly in return for payment.
The arrangement is believed to have been in place since 2010. Hanning is said to have used the confidential information to prepare, among other things, an analysis for foreign services and to earn private income as a consultant.
"Presumably in spring 2010, the defendants agreed that Manfred D.would continuously obtain valuable intelligence from the Federal Intelligence Service for the accused Hanning in return for payment," senior public prosecutor Dr Ines Peterson said.
Hanning is alleged to have used the material for private consulting work. Investigators bugged Manfred D's property and monitored him for months in a high-profile probe.