Cameron told MPs: "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.

"The approach we have taken is to try to talk to the press and explain how damaging some of these things can be and that is why the Guardian did actually destroy some of the information and disks that they have. But they've now gone on and printed further material which is damaging.

"I don't want to have to use injunctions or D notices or the other tougher measures. I think it's much better to appeal to newspapers' sense of social responsibility. But if they don't demonstrate some social responsibility it would be very difficult for government to stand back and not to act."