Amnesty International has warned that alleged mass surveillance by the American intelligence agency NSA could have placed its staff in danger.

Yesterday the former US intelligence contractor and whistleblower, Edward Snowden, was asked by the Parliamentary Assembly of the Council of Europe in Strasbourg whether the National Security Agency (NSA) deliberately spied on human rights organisations like Amnesty International and Human Rights Watch.

Speaking via a video link from Moscow Snowden said: “The NSA has in fact specifically targeted the communications of either leaders or staff members in a number of purely civil or human rights organisations of the kind described.”

Amnesty International’s senior director of international law and policy, Michael Bochenek, said: “These allegations, if substantiated, would confirm our long-held fears that state intelligence agencies like the NSA and GCHQ have been subjecting human rights organisations to mass surveillance all along.

“This raises the very real possibility that our communications with confidential sources have been intercepted. Sharing this information with other governments could put human rights defenders the world over in imminent danger.”

He called for “a full and frank disclosure of the extent of these surveillance programmes as well as watertight guarantees against such indiscriminate surveillance in the future”.

Explaining its decision to invite Snowden to testify, the Parliamentary Assembly of the Council of Europe said in a statement on Monday: "Edward Snowden has triggered a massive public debate on privacy in the internet age. We hope to ask him what his revelations mean for ordinary users and how they should protect their privacy and what kind of restrictions Europe should impose on state surveillance."