According to the magazine, Merkel's secret briefings with British security experts caused strong criticism among the German intelligence.
"Over the past twelve years, Merkel has not come to the weekly meetings of the heads of the German intelligence even once," a senior government told the magazine. "Why did she travel to England then? Doesn't she trust her own people anymore?" the source continued.
The last meeting between Merkel and representatives of the British intelligence took place in October 2015, 60 kilometers northwest of London in Chequers, in the residence of the then British Prime Minister, David Cameron.
Apart from Hannigan, the meeting was attended by head of MI5 Andrew Parker who is in charge of counterterrorism and counterintelligence activities, as well as head of MI6 Alex Younger.
According to Focus Online, Merkel provided the Brits with a BND dossier on Russian President Vladimir Putin and an analysis of the situation in Crimea in return.
The documents were prepared by a department of the Office of the Federal Chancellor, and German intelligence did not know anything about this either.