Heather Mills has told the Leveson inquiry that a message left on her phone by former husband Paul McCartney appeared to have been listened to by journalists.
Mills said that in 2001, after talking with then editor of Hello! magazine Phil Hal about a trip to Gujerat where she wanted to help with prosthetic limbs, she had an argument with McCartney and left to stay with a friend.
When she checked her phone Mills said she found dozens of "saved" voicemails.
"There were about 25 messages all asking for forgiveness over what had happened, which I won't go into. And if I would come back," she said, referring to her "former partner".
"One of them said "please forgive me" and sang a little ditty of one of his songs onto the voicemail.
"That afternoon I went back and all was forgiven."
"[The messages] were deleted pretty much straightaway," she said.
Later, Mills said, she was called by a Trinity Mirror employee who confronted her with the information from the messages. Counsel to the inquiry, Robert Jay QC, clarified that the person was not Piers Morgan or anyone employed by him
Mills said she told the employee: "I promise you if you report this story, even though it's true, you've obtained this information illegally and I will do something about it."
"And he laughed."
The news story was not published, but the incident is now the subject of a police investigation into phone hacking.
Former Daily Mirror and News of the World editor Piers Morgan has previously told the inquiry he listened to a voicemail message left to Mills by Sir Paul, but refused to say when or where he heard it because he wanted to protect a "source".
Mills said she had never authorised Morgan, or anybody, to access or listen to her voicemails, and neither had she ever played a recording to the former editor.
"I couldn't quite believe that he would even try to insinuate, a man that has written nothing but awful things about me for years, would relish in telling the court if I had played a voicemail message to him," she said.
Giving evidence in December, Morgan told the inquiry he would not disclose a source who played him a tape of a message that Sir Paul left Mills.
"I don't think it's right. In fact the inquiry has already stated to me you don't expect me to identify sources."
Lord Justice Leveson told him the only person who would be able to lawfully listen to the message was Mills or somebody authorised on her behalf.
He told Morgan: "I am perfectly happy to call Lady McCartney to give evidence as to whether she authorised you to listen to her voicemails.
"She may say she did in which case you're not compromising anybody, but if she didn't then we can proceed on the premise that it's somebody else, can't we."
Also appearing at the inquiry on Thursday, former News of the World news editor Ian Edmondson said that a "culture of bullying" had been created at the paper by former editor Colin Myler.
He said: "It's a case of you will do as you are told and you live in that environment."
"It's not a democracy at a newspaper," he added. "It's autocratic."
Edmondson also said he didn't "recall" writing emails appearing to threaten women to tell their side of a story involving Max Mosley.
The former boss of Formula 1 received £60,000 of damages after the NotW published a front page story about his encounter with five paid sex workers in London.
Mosley has since campaigned for the subject of newspaper stories to be given notice before publication. He gave evidence to the inquiry in November 2011.
The emails in question offered the women a chance to tell their story to the NotW anonymously, but also said the paper would publish their names and photographs without pixelation if they did not cooperate.
Other witnesses appearing at the Royal Courts of Justice in central London today include PR guru Max Clifford, Darryn Lyons, who founded picture agency Big Pictures, and general secretary of the National Union of Journalists, Michelle Stanistreet.
Prime Minister David Cameron set up the Leveson Inquiry last July in response to revelations that the News of the World commissioned a private detective to hack murdered schoolgirl Milly Dowler's phone after she disappeared in 2002.
The first part of the inquiry, which is now coming to an end, is looking at the culture, practices and ethics of the Press in general and is due to produce a report by September.
The second part, examining the extent of unlawful activities by journalists, will not begin until detectives have completed their investigation into alleged phone-hacking and corrupt payments to police, and any prosecutions have been concluded.