Guardian investigations editor David Leigh, who has been told that he will not be prosecuted for intercepting a phone message in 2006, has ruled out using phone-hacking again on a story.
Leigh, who first admitted hacking an allegedly corrupt arms executive in 2006, told the Leveson Inquiry the whole story last December.
But it wasn't until earlier this month that Leigh realised the Crown Prosecution Service (CPS) were investigating him. The CPS said there was no public interest in pursuing the case.
After hearing the news, Leigh, who first admitted to phone-hacking in a December 2006 Guardian article, told Press Gazette: "At the time I was not conscious that it was a criminal offence.
"Since then it's been made plain that it is a crime. I don't like the idea of going about committing criminal offences, so I wouldn't do it [hacking] again for that reason."
Leigh only found out a police investigation had been launched against him when the CPS called him on Thursday, 14 June, to say he would be receiving a letter from them.
The letter, which arrived 11 minutes later, said an investigation had taken place but that the CPS had decided he would not be prosecuted.
Leigh admitted that he was "startled" by the situation, assuming a line had been drawn under the incident after his appearance at the Leveson Inquiry in December.
"Leveson made it pretty clear that he agreed this was exactly the kind of public interest activity that shouldn't be prosecuted," he said.
"The comical thing was that everybody was saying, 'We didn't know you had this hanging over you - poor you'. The fact is I didn't know that I had it hanging over me either."
Leigh now suspects that someone from News International triggered the investigation, and he said he is unhappy with the way he has been treated by some journalists since he admitted to hacking six years ago.
Tom Newton Dunn, The Sun's political editor, tweeted Leigh asking whether he would now be defending News International journalists accused of similar practices.
Leigh replied: 'I'll back any arrested genuine 'public interest' NI journalist. But shame NI tried to have me arrested, isn't it?"
In the original 2006 article, he insisted he was "looking for evidence of bribery and corruption", not "witless tittle-tattle".
But he also admitted getting a "voyeuristic thrill in hearing another person's private messages", a statement that has been heavily scrutinised since.
"I was narked that all my non-friends at the Times and elsewhere seized on that phrase," he said.
"I said it because I was trying to get across how it was that tabloid journalists got addicted to doing this willy-nilly. It's a bit irritating to have it chucked back in my face."
He added: "I went on in the piece to say you should resist this kind of thing – you should only do it as a last resort."
Leigh defended the article but does regret the way it's "deliberately been misunderstood".
Looking back, he said his intention was for it to show the public how some journalistic investigations are carried out.
He also wanted to correct the misconception that The Guardian was "holier than thou".
"I work for a tough, professional organisation just like everybody else in Fleet Street," he said. "It's just we think there ought to be some laws about what's okay and what's not okay."
Asked if there were any situations where he felt it was in the public interest to hack phones, Leigh replied: "When you're investigating genuinely improper behaviour.
"I don't mean having sex with other people's spouses; I mean behaviour that's corrupt, criminal or damaging to democracy."
He added: "The reason we do things on the edge of the law is we don't have police powers to go around arresting people and we have to often use ingenious and undercover methods.
"It's only justified, as a last resort, when it's in the public interest."
Leigh insisted there is no legitimate public interest defence for some of the allegations involving News International journalists, highlighting the Milly Dowler case in particular.
He said: "If there was a way in which you could help find Milly Dowler by listening to her voicemails then that's what the police could do. You don't need News of the World to do it."