Britain's intelligence chiefs may have exaggerated the threat posed to national security by the leaking of files from America's National Security Agency files, according to a former lord chancellor.
Charles Falconer questioned whether the legal oversight of security agencies MI6, MI5 and GCHQ was "fit for purpose".
He said he was sceptical of the claim by the heads of the three British agencies that the leaks represented the most serious blow to their work in a generation, and warned that the NSA files highlighted "bulk surveillance" by the state.
Falconer pointed out that 850,000 people had access to the files even before they were leaked by NSA whistle-blower Edward Snowden.
Falconer, who as lord chancellor oversaw the administration of British courts from 2003 to 2007, said: "It seems to me to be inconceivable that the intelligence agencies in the US and the UK were not aware that it would not be possible to keep secret these sorts of broad issues for any length of time.
"If the position was that the US and the UK were intending to keep the general points secret then that seemed to me to be a very unrealistic position.
"Although I take very seriously what they say [about the importance of secrecy] I am sceptical that the revelations about the broad picture have necessarily done the damage that is being asserted."
In the interview, Falconer, who described himself as a strong supporter of the intelligence agencies from his time working with them during his decade in government, warned of "very, very serious questions" about whether the law has kept up with the rapid pace of technological change.
He also praised The Guardian and The New York Times, which formed a partnership to report on the leaked files, for working in a responsible way by alerting the agencies before publication.
"From all that I can see The Guardian and The New York Times have taken immense trouble to avoid any individual operative or operation being endangered."
The Guardian spoke to the NSA, the White House, the Department of Justice, GCHQ and the British government before publishing details from the leaked files.
Falconer, who is in charge of Labour leader Ed Miliband's preparations for government, is one of the most senior figures to question the account given by the intelligence chiefs this month to the British parliament's intelligence and security committee (ISC).
John Sawers, the chief of MI6, told the committee that the Snowden leaks had put operations at risk, adding that Britain's adversaries were "rubbing their hands with glee".
The Sunday Times on Sunday quoted a Conservative member of parliament describing the joint appearance by Sawers, the GCHQ director, Iain Lobban, and the MI5 director general, Andrew Parker, as a "total pantomime" after it emerged that they were told of questions in advance as part of a secret deal with the committee.
Lobban told the committee that his agents collect, though do not intercept, "innocent communications from innocent people" when they gather what he called the "haystack" of metadata.
Falconer said the Snowden revelations about the NSA raised questions about the intelligence agencies' work.