The Guardian played into the hands of terrorists by publishing stories based on information obtained by US whistleblower Edward Snowden, former foreign secretary Sir Malcolm Rifkind has said.
Sir Malcolm, who is currently chairman of the intelligence and security committee which scrutinises British intelligence agencies, the criticised newspaper's editor Alan Rusbridger, who he said was on "weak ground" and in no position to judge whether leaked information posed a national security threat.
Speaking on BBC Radio 4's Today programme, he said: "There's no question that the various press reports of some of the Snowden leaks - what Snowden has given to various newspapers in the United States and the United Kingdom - gave information about the way in which intelligence agencies are able to access emails or telephone calls by people who they suspect are terrorists - procedures that are much more sophisticated than perhaps terrorists understood.
"And terrorists, some of whom are very smart people, will have picked up that information and will have responded accordingly, and potentially made it more difficult if they have access to that information."
The Conservative MP for Kensington in London, who was foreign secretary (1995/97) and defence secretary (1992/95) under John Major, said journalists were unable to judge the potential security risks in using leaked information.
"Neither Mr Snowden nor the editor of the Guardian, or any other editor of any other newspaper, is in a position to necessarily judge whether the release of top secret information may have a significant relevance in the battle against terror and that these are very, very sensitive issues," said Sir Malcolm.
"Sometimes you may think - quite genuinely think - that it's not going to be of any assistance to terrorists, when in fact you may be wrong, and that's a question of your inability to judge, if you're a newspaper editor or a journalist, as opposed to somebody involved in the intelligence work that has to be done."
He added: "I think Mr Rusbridger and the article he wrote yesterday about the destruction of his hard disc is on relatively weak ground. He clearly did not dispute that he had no legal right to possess the files or the documents that were being discussed."
Sir Malcolm said the fact that Mr Rusbridger had "very sensibly" cooperated with the Government and allowed for the data to be destroyed was proof that he knew possession of the material was unlawful.
He defended Whitehall's destruction of the documents, despite Mr Rusbridger's claims that the newspaper had other copies.
Sir Malcolm said: "They may have been told by Mr Rusbridger that there were other copies elsewhere but they only have his word for that.
"As far as they're concerned, there was a top secret document, which the Guardian had in its possession. They wanted that back or they wanted it destroyed.
"The fact that Mr Rusbridger was claiming - he may be right, but we don't know that, nobody else knows that - that the documents also existed elsewhere, in another country, why should that be taken automatically as evidence of that fact? You can't take these risks when you're dealing with such matters of importance from a national security point of view."