Fresh privacy as well as legal concerns have been raised following revelations that UK intelligence agencies have been regularly spying on lawyers involved in sensitive security cases, breaching the privilege of lawyer-client confidentiality and handing an unfair legal advantage to the government in court. 

The disclosures were made at the Investigatory Powers Tribunal, which is hearing complaints about mass surveillance by GCHQ, a government intelligence agency. This latest information, after it was previously revealed at the Tribunal that GCHQ has been able to access large amounts of data without first obtaining a warrant, was obtained in documents submitted by GCHQ as well as the MI5 security service and MI6, officially the Secret Intelligence Service.

Government spies intercepted communications between lawyers involved in high-profile security cases and their clients, the documents show, potentially benefiting prosecutors in court. The documents were ordered to be released after two Libyan men, Sami al-SaadiAbdul and Hakim Belhaj, took legal action against the government for what they claimed was involvement in their rendition. 

The government said it would not comment on the revelations of official spying on lawyers' communications, citing the ongoing legal case and a policy of not commenting until after a verdict has been reached. 

Meanwhile, rights group Amnesty International, which is among a number of organisations that have brought the privacy case to the Tribunal, expressed alarm at the extent of the government's spying. The group's UK legal adviser, Rachel Logan, said it "clearly violates an age-old principle of English law: that the correspondence between a person and their lawyer is confidential."

She said it meant that the government could use information they obtained from spying on someone against them in legal proceedings that the person had launched, entirely upending the principle of a fair legal system. 

GCHQ, which stands for Government Communications Headquarters, has already been under intense national and international scrutiny after former American intelligence contractor Edward Snowden released secret files to the media showing mass surveillance on the public. It was revealed that GCHQ works closely with the US National Security Agency, which has also come in for severe criticism for its spying programmes.