Nick Clegg criticises Guardian for publishing spy secrets Lib Dem leader said readers would have been baffled by the leaks David Cameron backed the criticism of the Guardian's publication Nick Clegg today hit out at the Guardian for publishing secret files which served "no purpose" other than to aid terrorists who want to harm Britain. The Lib Dem leader joined the barrage of criticism that the newspaper released UK's intelligence secrets of no interest to readers but highly-valued by fanatics and foreign spies. It follows criticism of the newspaper from David Cameron and MI5 director-general Andrew Parker's warning this week that the leaks are a "gift" to terrorists. Criticism: In a highly-unusual move, Nick Clegg criticised the Guardian's decision to publish secret files which would only have been of interest to terrorists The publication of secret files leaked by US fugitive Edward Snowden are said to have caused huge "harm" to the capability of Britain's intelligence services. Security officials fear the data will be used by terrorists to avoid detection when plotting an atrocity. The Guardian has argued its revelations have "prompted a debate which was both necessary and overdue." But Mr Clegg rubbished the idea that highly-sensitive intelligence needed to be released in order to prompt discussions about the scale of the surveillance state. In an unusual attack on the left-wing newspaper, Mr Clegg said: "I think it's a totally legitimate debate about the power of these technologies, about how you get the balance right, how do you make sure these technologies are used in a proportionate and accountable way. What was published will have passed most Guardian readers completely by but would have been of immense interest to people who want to do us harm Deputy PM Nick Clegg But, I don't think just giving technical secrets, if I can put it that way, to people who want to do us harm serves any purpose. Speaking on his weekly phone-in on LBC 97.3, he added: "I've got no doubt that there were some parts of what was published which will have passed most readers of the Guardian completely by, because they were very technical, but would have been of immense interest to people who want to do us harm. 'I certainly agree that if what you end up doing is just basically publishing very technical information, that actually most Guardian readers, or most of us wouldn't frankly understand, but the only people who will understand are the sort of technicians if you like amongst the terrorists, then what's the public interest in that?' Mr Cameron stepped up his criticism of the Guardian today, insisting newspapers must 'think about their responsibilities' to national security. Speaking on a visit to York, the Prime Minister said: 'I think our intelligence and security services do a very good job of keeping us safe. 'Every year since I've been Prime Minister there has been one or two major plots that could have led to huge loss of life in our country and we rely on the intelligence services to help keep us safe. 'But when you get newspapers who get hold of vast amounts of data and information, which is effectively stolen information, and they think it's OK to reveal this, I think they have to think about their responsibilities and are they helping to keep our country safe.' He went on: 'To be fair to the Guardian, when I sent the Cabinet Secretary to tell them about how dangerous it was to hold this information, they agreed to have a whole lot of it destroyed. They have understood it on some occasions but they need to show understanding about this issue because it does go to our ability to fight terrorism. Warning: David Cameron, on a visit to Yorkshire today, said newspapers must 'think about their responsibilities' to national security In the Commons today Tory MP Julian Smith called for an urgent statement on the issue from Home Secretary Theresa May. Mr Smith said: 'As part of its reporting of national security issues, The Guardian has not denied sending the detailed family and personal information of our security agents across borders. That is illegal and it is threatening our agents and their families. He called for Mrs May we to 'clarify that the law will be upheld, whether or not the organisation involved is hiding behind the fig leaf of journalism?' The comments came after Mr Parker warned that the disclosure of the "reach and limits" of the GCHQ's capabilities was a gift to terrorists. In a speech this week Mr Parker said: "It causes enormous damage to make public the reach and limits of GCHQ techniques. Mr Parker dismissed suggestions that the agencies were trawling through people's private lives for anything that looked interesting as "utter nonsense." Yesterday David Cameron backed Mr Parker. Mr Clegg argued that secrecy was vital in order to keep the country safe. We have legislation, and regulations, which were designed for an age which is quite different now, and both terrorists and States and security agencies, now conduct this battle, if you like, online in a way that was unimaginable just even a few years ago. And, what that means for privacy and proportionality, I think that's a totally legitimate area for debate. How you hold the secret parts of any State to account is an incredibly important issue, because secrecy is necessary, of course it is, you absolutely must defend the principle of secrecy from the intelligence agencies without which they can't keep us safe. But, you can only really make secrecy legitimate in the eyes of the public if there is proper form of accountability. Guardian editor Alan Rusbridger denied putting lives at risk and - defying security officials - said he would continue publishing top secret information, which the paper has been splashing across its front pages since June. In an interview yesterday he said: "We are working slowly and responsibly but as we discover further stories that we think merit the debate, the debate that everyone says is necessary, then we will go on publishing."