Privacy International has released previously confidential government documents that shed light on how British spy agencies circumvented legal restraints on their surveillance powers, with little interference from the commissioner charged with overseeing them.

The documents detail correspondence carried out in 2004 between lawyers for two UK spy agencies — the Government Communications Headquarters (GCHQ) and MI5 — and Sir Swinton Thomas, the Interception of Communications Commissioner at the time. Thomas was responsible for overseeing the two agencies, but Privacy International, a London-based watchdog organization, says his correspondence with the GCHQ and MI5 "exposes the lack of meaningful restraint of the agencies' over-reaching and intrusive powers."

A "troubling history of bending the rules."

The release of the document comes ahead of a Parliamentary debate on the controversial Investigatory Powers (IP) Bill. Introduced last year, the bill aims to provide a legal framework for bulk data collection, while increasing transparency and strengthening oversight for British spy agencies. But privacy advocates, internet service providers, and major technology companies have expressed alarm over the law — referred to by critics as the "snooper's charter" — arguing that it gives police and intelligence agencies broad surveillance powers under vaguely defined terms.

Privacy International says that the correspondence released today demonstrates the flimsiness of existing oversight mechanisms. In one letter, the Home Office urged Thomas to authorize MI5's data collection for a "database project" under a 1984 telecommunications law rather than the Regulation of Investigatory Powers Act 2000 (RIPA), which would have required more transparent processes and safeguards. Thomas initially expressed reservations about the authorization, but eventually conceded, citing the "considerable... inconvenience" that RIPA would entail.

GCHQ also asked Thomas to authorize collecting communications data under the section 94 of the Telecommunications Act, and the commissioner eventually agreed, writing: "As you say, adhering to the spirit of the legislation is important." Home Secretary Theresa May acknowledged in a speech last year that section 94 has been used to authorize data collection in the past.

"an illuminating example of how oversight can go wrong."

Today's release comes nearly two months after Privacy International released previously confidential documents describing how MI5, MI6, and GCHQ have been conducting widespread surveillance, even on people who are "unlikely to be of intelligence or security interest." The documents were obtained as part of a legal claim that the watchdog group filed against the GCHQ earlier this year.

"The documents revealed today demonstrate the government's troubling history of bending the rules to expand its surveillance powers while minimizing safeguards," Caroline Wilson Palow, general counsel at Privacy International, said in a statement Monday, describing the correspondences revealed today as "an illuminating example of how oversight can go wrong when it lacks sufficient transparency and resources."

Sir Stanley Burnton, the current interception commissioner, tells The Guardian that his office has conducted a "comprehensive review" of how section 94 has been used to authorize communications since the late 1990s. He added that a forthcoming report "sets out an extensive series of recommendations which must be implemented in order to clarify and bring consistency to the procedures in place, remedy the lack of record-keeping requirements and codified processes and ensure that we are able to undertake this additional oversight and audit of the giving and use of section 94 directions properly."