The fallout continued yesterday after the revelation that MI5 and GCHQ routinely spied on privileged lawyer-client conversations.

On Thursday the government was forced to release secret documents showing it advised staff at the agencies that they “may in principle target the communications of lawyers.”

The documents were disclosed as part of case brought to the Investigatory Powers Tribunal by the families of two Libyan opponents of Colonel Gaddafi — Abdel-Hakim Belhadj and Sami al-Saadi, who were subjected to rendition, along with their families, and torture by the CIA with the alleged complicity of Britain in 2004.

The government had previously argued that disclosure of the material would compromise national security.

Amnesty UK legal adviser Rachel Logan said: “We now know that the government sees nothing wrong in routinely spying on the confidential communication between lawyers and clients.

“This clearly violates an age-old principle of English law set down in the 16th century that the correspondence between a person and their lawyer is confidential.

“It could mean, amazingly, that the government uses information they have got from snooping on you against you, in a case you have brought.”

London Assembly member Jenny Jones said the disclosure raised questions over whether the Metropolitan Police had also snooped on privileged conversations.

Ms Jones said: “The disclosure that the security services may in principle target the communications of lawyers raises questions about whether the Met has been snooping on lawyers. We know the Met used RIPA (Regulation of Investigatory Powers Act) to get journalists’ sources, so I wouldn’t be surprised to see them spy on lawyers and their clients, especially as the police don’t regard the data gathered as compromising legal privilege.”