Traitor Edward Snowden has revealed he did not read all the top-secret intelligence documents he leaked – a move which put lives at risk from terrorists.

In a television interview the fugitive squirmed as he admitted only ‘evaluating’ the files stolen from GCHQ and the US National Security Agency.

The former US spy also acknowledged there had been a ‘f***-up’ when newspapers that were handed the classified material failed to redact sensitive details exposing operations against Al Qaeda.

Scroll down for video

Last Week Tonight host John Oliver flew to Moscow to grill Edward Snowden about the leaking of 'harmful' documents and asks him to explain why he did it

But in an outburst of arrogance, Snowden said such potentially catastrophic blunders were a ‘fundamental’ price of liberty.

The 31-year-old stunned the world in June 2013 – less than a month after the murder of Lee Rigby by Islamic extremists – when he broke cover as the civilian CIA worker who stole classified documents.

He leaked information about attempts by spying agencies including GCHQ and the NSA to view citizens’ private information, claiming internet history, emails, text messages, calls and passwords were harvested.

But security chiefs have warned that secret techniques, revealed by Snowden’s leaks to the Guardian newspaper, have made it easier for terrorists and organised criminals to avoid detection.

Last month, Home Secretary Theresa May attacked the harm done by the traitor – now one of the world’s most wanted men. Terror experts said lives were being lost because he had hampered security service operations. They warned that extremists had altered their tactics after he leaked details from intelligence agencies – with fatal results.

In Sunday night’s interview with British TV host John Oliver, for US channel HBO, Snowden pointedly avoided saying he had read every document he handed over to journalists.

At one point the British comedian asks Snowden whether he had read all of the documents he sent to journalists. The whistleblower said he had an 'understanding' of their content

He would only say: ‘I’ve evaluated all of the documents that are in the archive.’ Pressed, he added: ‘I do understand what I turned over.’

But he acknowledged ‘recognising the concern’ over whether he knew enough about the contents of the files or the abilities of reporters to protect classified details.

Snowden admitted there had been a ‘f***-up’ with the way in which some of the information about the NSA and GCHQ, Britain’s intelligence agency, had been released.

Last year, the New York Times published a slide containing the name of the NSA employee who prepared it. The target of the surveillance was also identified as Al Qaeda in Mosul, Iraq.

Snowden said such details should have been removed and, in a feeble attempt to defend his actions, added: ‘In journalism we have to accept that some mistakes will be made. This is a fundamental concept of liberty.’

Unconvinced, Mr Oliver replied: ‘You’re giving documents with information that you know could be harmful which could get out there … We’re not even talking about bad faith, we’re talking about incompetence.’

Oliver tries to get Snowden to explain the leak in the context of nude pictures. The ex-CIA systems administrator claims the government can see most of the pictures you share

It is one of the few occasions in which Snowden has been put on the spot over his treachery as he normally speaks only to Left-wing media who have published his leaks.

Lord West, a former First Sea Lord and security minister, said: ‘Since the revelations of the traitor Snowden, terrorist groups have changed how they communicate and talk to each other.

‘His actions have made us all less safe. No doubt people will die who would not have died had he not been so irresponsible.’

Robin Simcox, of the Henry Jackson Society security think-tank, said: ‘This is exactly the danger that those who believe Snowden’s actions were hugely irresponsible – and potentially fatal – warned of.

‘This interview seemed to show how little Snowden had thought about the potentially deadly consequences. Snowden stole a huge amount of sensitive documents and as a result terrorists and other serious criminals have adapted their methods accordingly.’

Snowden handed an estimated 200,000 of the 1.7million stolen classified documents to journalists. In June 2013, he told the Guardian: ‘I carefully evaluated every single document I disclosed to ensure that each was legitimately in the public interest.’

'MISTAKES WILL BE MADE'... CONTEMPT OF EX-SPY SNOWDEN This is a transcript of Snowden’s interview: John Oliver: How many of those documents have you actually read? Edward Snowden: I’ve evaluated all of the documents that are in the archive. Oliver: You’ve read every single one? Snowden: I do understand what I turned over. 'These things happen': Edward Snowden, above, during his television interview Oliver: There’s a difference between understanding what’s in the documents and reading what’s in the documents. Snowden: I recognize the concern. Oliver (cuts in sarcastically): Right, because when you’re handing over thousands of NSA documents, the last thing you want to do is read them. (laughter) Snowden: I think it’s fair to be concerned – did this person do enough, were they careful enough? Oliver (cuts in): Especially when you’re handling material like we know you’re handling. Snowden: In my defence I’m not handling anything any more. That’s been passed to the journalists and they’re using extraordinary security measures to make sure this is being reported in the most responsible way. Asking the Questions: John Oliver Oliver: But those are journalists with a lower technical skill set than you. Snowden: That’s true but they do understand like you and I do just how important it is to get this right. Oliver: The New York Times took a slide, it didn’t redact it properly and in the end it was possible to see that something was being used in Mosul on Al Qaeda. Snowden: That is a problem. Oliver: Well, that’s a ****-up. Snowden: It is a ****-up and these things do happen in reporting. In journalism we have to accept that some mistakes will be made. This is a fundamental concept of liberty. Oliver: Right, but you have to own that then. You’re giving documents with information that you know could be harmful which could get out there. Snowden: Yes, if people act in bad faith. Oliver (cuts in): We’re not even talking about bad faith, we’re talking about incompetence. Snowden: We are, but you will never be completely free from risk if you’re free. The only time you can be free from risk is when you’re in prison. Advertisement

He added: ‘There are all sorts of documents that would have made a big impact that I didn’t turn over, because harming people isn’t my goal.’

A report by the Henry Jackson Society last month revealed terror suspects were using human couriers instead of email and phones following the leaks by Snowden. Daily operations of British spies have been damaged, with Islamic State seizing on the information – making it harder to track down its operatives.

Al Qaeda militants are known to have changed communication methods to avoid detection, and have produced a video advising fellow extremists on the matter.

GCHQ has lost track of some of Britain’s most dangerous criminals because of the way Snowden exposed its operations. Officials had to stop monitoring drug gangs, paedophiles, human traffickers and money launderers.

The agency has also been forced to tone down or abandon surveillance amid fears the tactics are too easy to spot and could force criminals to fall off the radar.

Mrs May told the Commons home affairs committee that the leaks ‘did cause damage’, adding: ‘It has had an impact on the ability of our agencies to do the work they need to do.’

Snowden, who was a computer specialist at an intelligence centre in Hawaii, tricked colleagues into handing over passwords so he could copy files in one of the biggest leaks in US history.

He claims he had to act because the US government’s policies were a ‘threat to democracy’. He fled to Hong Kong, then Russia, where he was granted asylum and now lives in a secret location.

A Guardian spokesman said the newspaper had ‘nothing to add’ in response to Snowden saying he had ‘evaluated’ the documents and whether this had put people at risk.

How the Guardian changed headline to protect its favourite 'whistleblower'

The Left-wing Guardian newspaper climbed into bed with Edward Snowden when he leaked the top-secret intelligence documents, publishing a string of damaging stories.

And yesterday it was still giving the so-called whistleblower an easy ride when reporting on his clash with TV host John Oliver on his US show Last Week Tonight.

The initial story on the Guardian website focused on the sensational revelation that Snowden had apparently not read all the documents. The headline stated: ‘Edward Snowden tells John Oliver he did not read all leaked NSA material.’ It added: ‘The whistleblower admits his actions carried dangers.’

But within hours it had toned down the headline so it focused less on his irresponsibility and incompetence. It was changed to: ‘John Oliver presses Edward Snowden on whether he read all leaked NSA material.’

The sub-heading was amended, to the softer: ‘HBO host posts uncomfortable questions to NSA whistleblower in interview in Moscow.’ A Guardian spokesman said the headline was changed because ‘an earlier version stated that Edward Snowden admitted he had not read all the NSA documents he leaked. In fact he did not answer that question’.