Media playback is unsupported on your device Media caption Mr Cameron said the cabinet secretary had "politely" asked the newspaper to destroy the data

The Guardian knows it compromised national security when it used data leaked by ex-US intelligence worker Edward Snowden, David Cameron has said.

At Prime Minister's Questions, Mr Cameron argued that "what has happened has damaged national security".

The newspaper had since effectively accepted its culpability by destroying the data when asked, he suggested.

The Guardian has said that it complied with the request to destroy the data because it had other copies.

Mr Cameron told MPs: "I think the plain fact is that what has happened has damaged national security, and in many ways the Guardian themselves admitted that when they agreed, when asked politely by my national security adviser and Cabinet Secretary [Sir Jeremy Heywood], to destroy the files they had, they went ahead and destroyed those files.

"So they know that what they are dealing with is dangerous for national security."

'Shadowy Whitehall figures'

He was responding to a question from Conservative MP and former Defence Secretary Liam Fox.

Mr Fox had asked the Mr Cameron: "Can we have a full and transparent assessment about whether the Guardian's involvement in the Snowden affair has damaged Britain's national security?

"And does my right honourable friend agree that it is bizarre that, from some, the hacking of a celebrity phone demands a prosecution, but leaving the British people and the security personnel more vulnerable is opening a debate?"

Mr Cameron replied: "I think it's up to select committees in this House if they want to examine this issue and make further recommendations."

Guardian editor Alan Rusbridger said last week that he planned to publish more revelations from Edward Snowden, despite warnings from MI5 that such disclosures cause enormous damage.

Mr Rusbridger insisted the paper was right to publish files leaked by the US intelligence analyst and had helped to prompt a necessary and overdue debate.

He had previously claimed that "shadowy Whitehall figures" had threatened to take legal action aiming to block further publication of the material.

They had demanded that he hand over the data or destroy it, he said.

"Given that there were other copies and we could work out of America, which has better laws to protect journalists, I saw no reason not to destroy this material ourselves rather than hand it back to the government," he told the BBC in August.