Gerhard Gribkowsky contacted the BND, Germany's foreign intelligence agency or Bundesnachrichtendienst, when he claimed Bernie Ecclestone was threatening him.
That is the latest bombshell to emerge this week from F1 chief executive Ecclestone's bribery trial in Munich.
According to German reports, the details were presented to the court by the 83-year-old Briton's lawyers, as jailed Gribkowsky's credibility continues to come under attack.
Ecclestone faces the loss of his job in F1 and even jail as prosecutors try to prove he bribed Gribkowsky to the tune of $44 million over the sale of the sport's commercial rights some years ago.
Ecclestone's defence is that the payment was in fact hush money because Gribkowsky was threatening to make allegations to the British authorities about his personal tax affairs.
But as it emerged in court on Tuesday, it was Gribkowsky who was alleging that Ecclestone posed the real threat.
Written documents show that Gribkowsky, then chief risk officer at former F1 shareholder and state Munich bank BayernLB, asked his secretary to contact the head of the intelligence agency BND.
Gribkowsky reportedly alleged suspicious observations while jogging, and mysterious knocks at his door, which he also reported to police in late 2004, claiming it was linked to pressure being applied by Ecclestone around the time of the F1 rights sale.
A witness testified on Tuesday: "I thought it was telling that he (Gribkowsky) spoke about it (the alleged Ecclestone threat) so often."