Germany's federal police chief, Jörg Ziercke, was forced to admit to MPs at the Bundestag that not only had Kennedy had a long-term lover in Berlin – in direct violation of a law forbidding police officers to have sexual relationships while undercover – but that he had been invited to Germany by the authorities to infiltrate the anti-fascist movement.

Ziercke also revealed that Kennedy, the Metropolitan police officer at the centre of a controversy over the infiltration of peaceful environmental groups across Europe, worked for three German states during at least five visits to the country between 2004 and 2009.

He said the agent committed at least two crimes, but the cases against him were dropped at the behest of German authorities who knew Kennedy's true identity.

Kennedy first broke the law during protests at Heiligendamm, the town near Rostock where the G8 meetings took place in 2007. He later committed arson, Der Spiegel said, during a demonstration in Berlin at which he set fire to containers.