English comedian John Oliver has probed exiled American whistleblower Edward Snowden in an unusually tough interview by the television funnyman.

Best known for his hilarious expletive-laden rants about people like Tony Abbott on his hit US talk show Last Week Tonight With John Oliver, the comedian can now add hard-hitting journalism to his resume.

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In the secret interview filmed in Moscow last week, Oliver challenged 31-year-old Snowden over his role in leaking thousands of classified documents about American government surveillance programs in 2013.

“Yes, last week, I spent 48 paranoid hours in Moscow,” Oliver said, describing Snowden as “the most famous hero and/or traitor in recent history”.

While award-winning documentaries have been made about the computer analyst, who now resides in Russia, it took an encounter with the bespectacled comedian to make Snowden squirm.

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After banter about how much he missed America, it didn’t take long for the grilling to begin and for Snowden to slip up and expose some past lies.

“How many of those documents have you actually read?” Oliver asked, referring to the estimated 200,000 documents Snowden shared with Hong Kong media.

Taken aback, Snowden mumbled “I do understand what I turned over”.

Oliver wasn’t impressed, and called on the analyst to take responsibility for the damage the leaks had caused.

“There’s a difference between understanding what’s in the documents and reading what’s in the documents… because when you’re handing over thousands of NSA [National Security Agency] documents the last thing you’d want to do is read them,” he said.

“So The New York Times took a slide, didn’t redact it properly, and in the end it was possible for people to see that something was being used in Mosul on al Qaeda.”

When Snowden said it was a “problem”, Oliver went further and called it a “f***up”.

“You’re giving documents with information you know could be harmful, which could get out there,” he said.

The interview was still peppered with plenty of humour, with Oliver asking Snowden if the security agency could access people’s nude photos.

“Well, the good news is there’s no program named ‘the d**k pic program’,” Snowden revealed.

“This is something that’s not actually seen as a big deal in the culture of the NSA, because you see naked pictures all the time.”