British intelligence agencies have disclosed that spies are allowed to intercept communications between lawyers and their clients, which are generally protected by strict rules of confidentiality.

Lawyers for the intelligence service have published previously secret details of the guidelines for spying on lawyers. They tell staff "you may, in principle, target the communications of lawyers."

The information was disclosed in court documents after a request from lawyers for two Libyan men who have sued the British government for alleged complicity in their detention and rendition.

The agencies say their guidelines stress that their lawyers cannot see material about cases in which they are involved.

But Cori Crider, a lawyer for the Libyans and their families, said Thursday that the revelation "raises troubling implications for the whole British justice system."