David Cameron threatens Guardian with legal action over PRISM spy leaks

David Cameron has threatened the Guardian with legal action in an effort to prevent them from publishing further leaks from whistleblower Edward Snowden.

Singling out the Guardian in a statement to MPs on Monday, the Prime Minister urged the newspaper to show "social responsibility" when reporting on revelations about Government Communications Headquarters (GCHQ), or else risk "injunctions or D-Notices or other tougher measures."

Cameron warned that the use of injunctions or D-notices – an official request from the government to news editors to not publish certain material in the interest of national security – would be unavoidable if newspapers did not follow the advice of the government.

"We live in a free country so newspapers are free to publish what they want," Cameron said, "We have a free press, it's very important the press feels it is not pre-censored from what it writes and all the rest of it."

However, he then went on to add, "If they don't demonstrate some social responsibility it would be very difficult for the government to stand back and not to act."

He also argued that the continued publication of such material by The Guardian and other newspapers would affect the UK's relationship with the United States.

"The UK has a very strong, long standing trust based relationship with the United States," he said, "not least as part of the 'Five Eyes' partnership."

GCHQ's involvement in the NSA-led PRISM scheme of mass-data collection has been heavily criticised in the wake of the Guardian's publication of the leaks, though David Cameron has showed continued support for their actions.

Earlier this month the prime minister defended the activities of British intelligence agencies on ITV's The Agenda, arguing that snooping "keeps us safe."

"We have very good rules in this country," he said, "I'm satisfied we have pretty strong safeguards. I thought part of the reaction to the The Guardian story was - big surprise, spies learn to spy."

Cameron's latest statement came on the same day that Spanish newspaper El Mundo published reports that the NSA-led PRISM scheme tracked 60 million Spanish phone calls in a single month.