The most damaging allegation about the former model is that she was a high-class prostitute who had sex with an arms dealer, Adnan Khashoggi, and was paid up to £10,000 a night for sleeping with rich men.
Under the headline "Heather the £5,000 hooker", the News of the World claims that the anti-land mines campaigner amassed a "secret fortune" from sleeping with clients.
The latest revelations seem to be part of what media watchers say is a deliberately orchestrated attempt to discredit the former model, who has always had a difficult relationship with the press.
The Sun published pictures last week of lady Mccartney posing naked for what they described as a German "hard core porn" book. Her publicist attempted to play down the images by saying that the book was a sex educational manual.
The Mail on Sunday and the Sunday Mirror newspapers carry interviews this weekend with Peter Wilson, the man who posed with her in the photographs. He describes the book that they simulated sex acts for as "cheap, titillating and sleazy" and says that Lady McCartney was "unashamed and unabashed".
The People, meanwhile, is sympathetic to Sir Paul's estranged wife who is reported to be still in pain following an operation on her amputated leg. The story reveals that she has lost 14 pounds since the separation.
This is the latest in a string of increasingly lurid stories to emerge about 38-year-old Lady McCartney, who separated from Sir Paul six weeks ago and is now involved in a high-profile divorce from the 63-year-old former Beatle, which involves custody of their daughter, Beatrice.
The couple married in June 2002 and their daughter was born a year later. The couple are currently negotiating the size of Lady McCartney's divorce settlement from Sir Paul, who is thought to be worth more than £800m. Sir Paul has repeatedly said he is concerned for his wife and that the couple speak several times a day.
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