Former Daily Mirror editor Piers Morgan has told the Leveson Inquiry he was not aware of any phone hacking taking place at the paper while he was in charge.
Speaking via video link, he told the media ethics hearing: "I have no reason... to believe it was going on."
Mr Morgan admitted hearing a recording of a message from the phone of Sir Paul McCartney's former wife but would not say who had played it to him.
He said he was not "directly involved" in the use of private investigators.
Mr Morgan was the Mirror's editor between 1995 and 2004. He also edited the News of the World (NoW) between January 1994 and November 1995.
He denied suggestions that phone hacking was "endemic" at the Mirror.
"Not a single person has made a formal or legal complaint against the Daily Mirror for phone hacking," he told the inquiry.
Robert Jay QC, counsel to the inquiry, asked Mr Morgan about the recording of a voicemail message left by former Beatle Sir Paul for his then-wife Heather Mills, when the couple were suffering marriage problems.
Addressing the London hearing from the US, where he is a TV presenter for CNN, Mr Morgan said he had listened to a tape of Ms Mills' message but said: "I can't discuss where that tape was played or who made- it would compromise a source."
Inquiry chairman Lord Justice Leveson said he was happy to call Ms Mills to see whether she had granted permission for the message to be listened to.
Mr Morgan said: "All we know for a fact about Lady Heather Mills McCartney is that in their divorce case Paul McCartney stated as a fact that she had recorded their conversations and given them to the media."
When asked if it was unethical to listen to phone messages, Morgan said: "It doesn't necessarily follow that listening to someone else talking to someone else is unethical."
He was asked about an investigation by the Information Commissioner's Office which found that 45 Mirror journalists were mentioned in the files of private investigator Steve Whittamore.
Mr Morgan said the use of private investigators was organised through the news or features desk and that he would not have been directly involved.
"All journalists knew they had to operate within the law. That was enshrined in their contracts of employment," he said, adding: "The average editor is probably aware of about 5% of what his journalists are up to at any given time."
Mr Morgan also said he had never been aware of police officers being paid for information while he was at the paper.
He was asked about his book The Insider: The Private Diaries of a Scandalous Decade, in which he says he became aware of phone hacking in 2001.
He told the inquiry: "The Fleet Street rumour mill, which is always extremely noisy and not entirely accurate, was buzzing with rumours that it spread a lot further than Clive Goodman. I do think he was made a scapegoat and, having known him at the News of The World, I felt sorry for him."
Mr Morgan was also questioned about his view on the issue of privacy. "I have very little sympathy with celebrities who sell their weddings for a million pounds - one of the most private days of their lives - and then expect to have privacy if they get caught having affairs," he said.
At the end of his evidence Mr Morgan said that he felt "like a rock star having an album brought out from his back catalogue about all his worst-ever hits".
He said the inquiry was ignoring a lot of newspapers' best work, adding: "I do feel still very proud of a lot of the very good stuff that both the Mirror and the News of the World did during my tenure as editor.
Earlier Steve Turner, general secretary of the British Association of Journalists, had described to the inquiry a culture of "bullying" at some newspapers.
If people turned up at News International accompanied by a union rep they would have had their "card marked", he said.
"I'm ashamed to be telling you this because we are supposed to be living in a free, democratic country but we are not.
"We are living in a society where people are wage slaves and treated very badly and that's the circumstance I found at the News of the World."
Former News of the World TV editor Sharron Marshall told the inquiry there were some managers who were not ideal and there could be dispute over the way a story was handled.
But she added: "I wouldn't say there's a culture of bullying... maybe you have a disagreement about how story is (done)."
Tuesday's hearing had begun with Julian Pike, partner at a law firm used by NoW owner News International, being recalled to the inquiry to explain how he knew actress Sienna Miller was going to make a claim against the now-defunct newspaper before it became public.
He supplied the inquiry with emails from various parties involved and a letter from the Metropolitan Police relating to the matter.