Beefed up safeguards should be in place before communications between lawyers and their clients are spied on, the UK’s terror watchdog said in a report on the future of Britain’s surveillance laws.

In a 373-page report, A Question of Trust, David Anderson QC accepted that security and intelligence agencies should have powers to carry out bulk collection of personal communications, but called for greater safeguards in the use of such data.

He recommended that the power to authorise “novel or contentious” requests to intercept communications should move from the hands of minsters to a judicial commissioner, under a new body called the Independent Surveillance and Intelligence Commission.

Acknowledging the importance of legal privilege as the “cornerstone of a society governed by law”, he said special restrictions should apply in relation to communications between lawyers and their clients, with similar considerations for journalists and others who handle privileged information.

The government-commissioned report to examine how the law in this area should be modernised, came in the wake of former US spy Edward Snowdon’s revelations about surveillance.

It was published a few days after two MPs, Labour’s Tom Watson and Conservative David Davis, began their High Court challenge to the legality of the Data Retention and Investigatory Powers Act (DRIP).

The pair, backed by human rights group Liberty, claim that the emergency law, rushed through Parliament last July, is incompatible with the right to respect for private and family life, and to data protection, under the Human Rights Act and the European Charter of Fundamental Rights.

Bar Chairman Alistair MacDonald QC commented that DRIP and its predecessor, the Regulation of Investigatory Powers Act, require “urgent revision” by Parliament.

“Together they have given dubious legal authority to security services to listen in on communications between lawyers and clients. This undermines legal professional privilege, one of the most important safeguards protecting the fairness of a trial and a doctrine that has existed as a constitutional principle for centuries,” he said.

If the state eavesdrops on privileged communications to gather intelligence, he said clients will feel unable to speak openly with their lawyers. “This has the potential result that defence teams will not even know about perfectly proper defences open to a defendant and will therefore not be able to advance them at trial.”