The British ambassador in Berlin has been called in to Germany's foreign ministry to respond to spying allegations.
The UK's Independent newspaper said the British embassy in Berlin may house a top-secret listening post.
It cited leaked US National Security Agency (NSA) documents suggesting the UK could be using hi-tech equipment housed on the embassy roof. Berlin said any such activity would be against international law.
A spokesman for David Cameron said the prime minister had not spoken to Chancellor Angela Merkel about the spying allegations and there were no plans for a conversation, although their relationship is intact. He refused to comment on security issues but said Britain's intelligence services operated under a strong and clear legal framework.
And, Brazil's Minister of Justice has defended his country's spying activities, saying they were completely different from those carried out by the United States.
Jose Eduardo Cardoso said agents who photographed US, Russian and other diplomats in Brazil were acting lawfully. Allegations about agents' activities were leaked in the national press.
Reports of email and phone spying on Brazil have prompted President Dilma Rousseff to postpone a visit to the US.
Brazil's counter-intelligence reports have caught the attention of the international media, with the New York Times saying they put the country in an uncomfortable position after it had harshly criticised US authorities.