A leading British Conservative Party MP has written to Director of Public Prosecutions (DPP) Alison Saunders to ask whether the Guardian could be prosecuted for publishing material leaked by former US National Security Agency contractor Edward Snowden.

Dr. Liam Fox, a former defence secretary, asked if the newspaper had breached counterterrorism laws by disclosing mass surveillance by US and UK spy agencies.

Fox’s approach to the DPP marks a stepping up of the campaign of threats and intimidation against the Guardian that has seen it accused of aiding terrorists by publishing details of the illegal activities of the NSA and Britain’s Government Communications Headquarters (GCHQ).

Appearing before the Intelligence and Security Committee last week, the heads of GCHQ, the internal security service MI5 and foreign intelligence department MI6 repeatedly claimed that Snowden and the Guardian were jeopardising national security with their disclosures of US and UK agencies monitoring the Internet and phone activity of the majority of the world’s citizens.

The hearing was meant to demonstrate the spying agencies’ accountability to parliament, but served only to underscore the obsequiousness of the assembled MPs, with MI6 head Sir John Sawers claiming, “The leaks from Snowden have been very damaging. They have put our operations at risk.… Al-Qaida are lapping it up.”

In his letter to the DPP, Fox states, “In recent days there have been further accusations that the Guardian passed the names of GCHQ agents to foreign journalists and bloggers.

“Would such activities, if true, constitute an offence under the Terrorism Act 2000 or other related legislation, particularly the passing of details of identified security personnel?”

He continues, “Under what conditions and by what procedures would a decision be taken to prosecute any individuals responsible for such activities and how would such a process be initiated?”

The same day, Fox had a comment in the Daily Telegraph under the heading, “A free press, but not when it endangers the security of our nation.”

Referencing cross-party moves to enforce state regulation of the media—including the Internet—Fox argued for a balance between the right to free expression and the “right of the security services to penetrate our internet and other communications as part of their role to keep us safe from terrorist or criminal threats.”

Snowden “has seriously compromised the national security of his own nation and its allies,” he asserted. Addressing the police detention in August, under anti-terror laws, of David Miranda, partner of Glenn Greenwald, the former Guardian writer who worked closely with Snowden, Fox said he had been “acting as a mule carrying further information to Mr Greenwald on an airline ticket paid for by The Guardian .”

He went on to complain that the Guardian ’s editor had “exhibited no sense of understanding, never mind remorse about what damage might have been done to the safety of individuals or the country….”

Asserting that giving details “of named individual agents to overseas sources is likely to constitute a crime,” Fox threatened, “No one is above the law and when it comes to criminality, including laws on our national security, we all have to decide which side we are really on.”

Fox’s threats underscore the reactionary efforts being made to bully the Guardian, so as to conceal the extent to which the state and its agencies have traduced democratic rights and set in place the mechanisms of a police state. Last week, Conservative MPs Julian Smith and Stephen Phillips QC had asked the Guardian to say in “clear and unambiguous terms” whether it had allowed the files leaked by Snowden to be accessed by anyone overseas.

On Sunday, Foreign Secretary William Hague and Defence Secretary Philip Hammond endorsed the statements of the spy chiefs against Snowden and the Guardian.

Hammond told Sky News’s Murnaghan programme that Snowden’s disclosures had “undoubtedly” damaged Britain’s ability to fight terrorism. “Anything which gives away the trade craft, the methods, and the methodologies of the Security Services and the agencies, is of course hugely valuable to those who wish it harm,” he said.

Hague told the BBC’s Andrew Marr Show that the intelligence chiefs’ complaints over the Guardian revelations were “absolutely right.”

“The Snowden allegations, let me put it that way, certainly have endangered our national security, made it harder for us to protect our country and other countries from terrorist attacks,” he said.

Neither Hammond nor Hague would be drawn on whether legal action should result against the Guardian or anyone else, with both asserting that it was a matter for Attorney General Dominic Grieve.

On Monday, Home Secretary Theresa May became the latest cabinet minister to hit out at the Guardian. Speaking at the Society of Editors annual conference in London, May said that anything that “potentially gives help to terrorists” is something the government “needs to be concerned about and act on”.

Asked by former BBC executive Phil Harding whether an editor who is leaked intelligence material should “look at it, consider publishing it, or merely walk to the nearest police station and hand the memory stick over,” May responded by citing MI5 head Andrew Parker, who said Snowden’s leaks gave terrorists “the gift to evade us and strike at will”.

Asked by Harding who should make the judgement whether the information was in the public interest or should not be published for national security purposes, May sidestepped. “There is a process available” of deciding whether to publish, she said, noting that the Guardian had gone through “various processes” including “discussions with government at a senior level about that.”

“There is an onus on every editor looking at material of that sort to recognise their responsibilities as well as the natural desire to have a story in their newspaper,” she said. Guardian editor Alan Rusbridger is to appear before the House of Commons Home Affairs Select Committee next month.

Faced with the unprecedented campaign against it, the Guardian is trying to present itself as a model of “responsible” journalism, arguing that Snowden’s ability to get his hands on details of NSA/GCHQ spying has shown how lax the agencies security arrangements are.

In its editorial on the ISC hearing, the Guardian complained that the real intelligence disaster “was that the US agencies have, for the second time in three years, proved incapable of keeping enormous secret databases secure. After WikiLeaks it is astonishing that 850,000 people worldwide were able to peer into the heart of secret operations in Cheltenham.”

“The intelligence agencies were saved from true catastrophe by only one thing:” it continued, “the fact that Snowden didn’t dump the material on to the web, but handed it instead to journalists. Together with the New York Times and Washington Post, we have worked carefully and responsibly (in consultation with governments and agencies) to disclose a small proportion of what he leaked. Some would like newspapers gagged or prosecuted. Be careful what you wish for. Kick newspapers by all means, but, without them, be prepared for something much worse.”

Rusbridger underscored what the editorial meant by “something much worse”, in his response to the spy heads’ criticisms.

“Were newspapers to be injuncted, criminalised or inhibited from reporting on such matters...it is easy to predict what the next Edward Snowden or [fellow whistleblower] Chelsea Manning would do,” he said.

“They would, in all probability, bypass newspapers and publish the material directly on to the web, with far more serious consequences.”