Germany's foreign ministry has summoned Britain's ambassador in Berlin after reports the embassy was used as a secret listening post.
A report in The Independent claimed that documents from the US National Security Agency (NSA) together with aerial photos and information about past spying activities in Germany suggested Britain could be operating a spy station using equipment housed on the embassy roof.
Foreign minister Guido Westerwelle requested the attendance of Simon McDonald to respond to the claims.
A spokeswoman for the embassy confirmed the meeting had taken place but refused to give details. The embassy refused to comment on the report.
The head of the ministry's European department noted that "eavesdropping on communication from diplomatic premises would be against international law".
In diplomatic terms, the invitation is a step below last month's summoning of the US ambassador in Berlin following allegations that American intelligence may have targeted Chancellor Angela Merkel's cellphone.
Government officials reacted with outrage to the report, published by German magazine Der Spiegel and citing documents obtained through NSA whistleblower Edward Snowden.
German officials have since been sent to Washington to find out what surveillance the US conducted in Germany and to try to forge a "no spy" agreement between the two nations.
A spokeswoman for Germany's domestic intelligence agency said a group it set up after the first NSA spying allegations emerged in the summer is looking at the activities of British as well as US intelligence. She did not comment on any results, which go to a parliamentary committee.