Britain has been operating a secret listening post from its Berlin embassy, a stone's throw from German Chancellor Angela Merkel's office, the Independent newspaper claimed on Tuesday.
The report said Britain's electronic eavesdropping centre GCHQ (Government Communications Headquarters) appeared to be using high-tech equipment on the embassy roof to intercept German data.
The broadsheet cited aerial photographs and information about past spying activities in Germany, as well as documents provided by Edward Snowden, the former contractor with the US National Security Agency (NSA) who has fled to Moscow.
The report comes hot on the heels of a furor over claims that the United States tapped Merkel's mobile phone as part of worldwide surveillance operations.
A US eavesdropping post on the roof of the US embassy in Berlin is believed to have been shut down last week as Washington scrambled to limit damage from the row, the Independent reported.
The daily said Snowden's documents suggested GCHQ has worked with US agencies and other partners to operate a network of electronic spying posts from embassies around the world, intercepting data in host nations.
A spokeswoman for British Prime Minister David Cameron's office said: "We don't comment on intelligence matters."
The Independent printed photos showing an aerial view of the British and US embassies -- which are on the same block next to the Brandenburg Gate in central Berlin -- highlighting large white boxes that it said were the intercept "nests".
Thermal images of the US embassy provided by the German public broadcaster ARD allegedly show a significant reduction in activity between October 24 and October 25, when claims first emerged that Merkel's phone had been tapped.
ARD broadcast the images on October 27, saying that the top floor of the embassy possibly houses a listening 'nest'.
Washington's ties with key allies have been strained in recent weeks by leaks appearing to show that the US has eavesdropped on dozens of foreign leaders, as well as tapping tens of millions of European phone calls and data from Internet giants such as Google and Yahoo.
But while European states have expressed outrage over the apparent extent of US espionage operations, Britain's Guardian newspaper reported Saturday that German, French, Spanish and Swedish intelligence services collaborated with GCHQ to develop their own mass surveillance operations.
The Guardian said the European intelligence services, in a "loose but growing" alliance, carried out surveillance by directly tapping fibre-optic cables and through secret relationships with communications companies.