Hugh Grant has told the Leveson Inquiry into media ethics that the Mail on Sunday (MoS) may have hacked his phone.
The actor said he could not think of any other way it could have got its story in 2007 about his conversations with a "plummy-voiced" woman.
The MoS said it "utterly refutes" his claim, which it described as "smears".
Earlier, the mother of murdered girl Milly Dowler said she did not sleep for three days after discovering that her daughter's phone had been hacked.
Mr Grant's suggestion that the MoS may have hacked his phone is the first time he has linked a newspaper not owned by media tycoon Rupert Murdoch to the practice.
The article, which Mr Grant sued and won damages over, claimed his relationship with Jemima Khan was on the rocks because of his late night calls with a "plummy-voiced" studio executive from Warner Brothers.
"It was a bizarre story and completely untrue," he told the inquiry.
"Thinking about how they could possibly come up with such a bizarre, left-field story... I realised there was a great friend of mine in Los Angeles whose assistant is a charming, married middle-aged lady, who is the person who rings you instead of the executive.
"I cannot for the life of me think of any conceivable source for this story in the Mail on Sunday other than the voicemails that were on my mobile telephone."
Counsel to the inquiry, Robert Jay QC, said Mr Grant's claims were "pure speculation".
The MoS later firmly denied his account.
In a statement the paper said: "The Mail on Sunday utterly refutes Hugh Grant's claim that they got any story as a result of phone hacking.
"In fact in the case of the story Mr Grant refers to, the information came from a freelance journalist who had been told by a source who was regularly speaking to Jemima Khan.
"Mr Grant's allegations are mendacious smears driven by his hatred of the media."
Jemima Khan has in turn disputed the MoS version of events on twitter, saying it was not true that a source close to her told a freelance journalist about the "plummy voice woman".
"The first time I heard anything about this was when I read about it in the MoS," she said.
Mr Grant, who rose to fame with the 1994 film Four Weddings and a Funeral, also told the inquiry one paper in 1995 had described the inside of his London flat - shortly after it had been broken into.
"The front door had been shoved off its hinges. Nothing had been stolen, which was weird," he said.
"Shortly after that, a detailed account of what the interior of my flat looked like appeared in one of the papers. I remember thinking who told them that? Was that the burglar, or was that the police?"
The incident happened around the time of his arrest in Los Angeles with a prostitute, and the "press storm" that followed it.
He also said:
- The Sun and Daily Express had invaded his privacy by publishing details of his medical record he claimed they had "appropriated... for commercial profit"
- He had brought between six and 10 libel actions over the past 17 years
- He had accepted undisclosed libel damages in April 2007 over claims his relationship with Ms Khan was destroyed by a flirtation with a film executive and his behaviour around Liz Hurley's wedding
- He and girlfriends had been "chased at speed" by paparazzi
- He had experienced press intrusion over his relationship with Chinese actress Tinglan Hong, the mother of his baby daughter, when pictures were taken with a telephoto lens
Earlier, Mrs Dowler and her husband Bob were the first witnesses to give evidence and said the hacking of Milly's phone had given them false hope that she was still alive.
She said they had called the 13-year-old's phone repeatedly in the weeks after she went missing, but the voicemail had become full.
Mrs Dowler said she could access it again later on because some of the messages were deleted after the detective working for the News of the World (NoW) had hacked the phone number.
And she recalled telling friends "she's picked up her voicemail, she's picked up her voicemail".
She added: "When we heard about the hacking that was the first thing I thought."
The private detective concerned, Glenn Mulcaire, later issued a statement denying he had been responsible for deleting messages from Milly's mobile.
It was nine years later during the trial of their daughter's killer that they were told by police her phone had been hacked.
Milly was murdered after being abducted on her way home from school in Walton-on-Thames, Surrey, in March 2002.
Her killer - former nightclub bouncer Levi Bellfield - was found guilty in June 2011 and given a whole life prison tariff.
Mrs Dowler told the inquiry: "As soon as I was told it was about phone hacking, literally I didn't sleep for about three nights because you replay everything in your mind and just think, 'oh, that makes sense now, that makes sense'."
The couple also described how they were secretly photographed as they privately reconstructed Milly's last walk, seven weeks after she disappeared.
Mrs Dowler said: "We put out missing leaflets and a telephone number. That number had changed and I was checking to see if the right poster was up and I was touching the posters to see if they were the right ones.
"That Sunday, that photo appeared in the News of the World. I remember seeing it and I was really cross. They had obviously taken the photo with some sort of telephoto lens. How on earth did they know we were doing the walk on that day?
"It felt like such an intrusion into a really, really private grief moment."
Mr Dowler was asked what he would say to NoW publisher News International.
He told the inquiry: "We would sincerely hope that News International and other media organisations would look very carefully how they procure, how they obtain information about stories.
"Obviously, the ramifications are far greater than what appears in the press."
The inquiry also heard from Graham Shear, a lawyer who represents celebrities and who is an alleged victim of the practice himself.
He said he was shocked to discover that reporters had turned up outside his home moments before he was due to meet clients there.
He also said papers that published "kiss and tell" stories consciously assessed whether the potential costs in damages outweighed the revenues that could be gained through extra sales.
Writer and campaigner Joan Smith told the inquiry she believed her phone was hacked while she was in a relationship with the MP Denis MacShane.
She said: "The tabloid press seems to live in a 1950s world where everyone is supposed to get married and stay married and anything that happens outside that is a story.
"I think we have a tabloid press which is almost infantile in its attitude towards sex and private life."
Prime Minister David Cameron set up the inquiry before Lord Justice Leveson in July in response to revelations that the NoW hacked Milly's phone.