Guardian editor rebuffs MI5 chief's attack on Prism leaks

The editor of the Guardian, Alan Rusbridger, says he plans to publish more Prism spy scandal revelations, despite the head of MI5 claiming previous leaks have given terrorists the "advantage".

Rusbridger maintains that his paper's previous stories based on leaks from US National Security Agency contractor Edward Snowden had helped to prompt "necessary and overdue debate" on the way the secret services conduct their business.

Earlier this week MI5 head Andrew Parker claimed the Guardian revealing how the secret services worked to gather evidence on targets would hand an advantage to terrorists by helping them evade detection.

Rusbridger told the BBC: "If Parliament's not going to have this discussion and if the courts can only do this in private then I think absolutely it falls to the press to stimulate a discussion."

Rusbridger said his paper had revealed the "extent to which entire populations are now being potentially put under surveillance".

He told the BBC: "I just spent a week in America where everybody is talking about this, from the president down. It's quite surprising to me that the number of MPs in this country who have said anything at all in the last four months can be counted on one hand - Malcolm Rifkind, Tom Watson, David Davis."

When asked about Parker's earlier comments that the Guardian's revelations were helping terrorists, Rusbridger said: "They will always say that. You read histories of intelligence and you go back to the 1990s and the security people were saying the same."

Parker had said that what MI5 knows about the terrorists and the secret details of the capabilities it uses against them represents its "margin of advantage". That margin he said allows MI5 to detect their plots and stop them.

"But that margin is under attack," Parker said, implying that the Prism scandal, which has shone a light on MI5 and MI6 spying methods, is eroding it. "GCHQ [the secret service national listening centre] intelligence has played a vital role in stopping many of the terrorist plots that MI5 and the police have tackled in the past decade.

"It causes enormous damage to make public the reach and limits of GCHQ techniques. Such information hands the advantage to the terrorists. It is the gift they need to evade us and strike at will. Unfashionable as it might seem, that is why we must keep secrets secret, and why not doing so causes such harm."