A Scottish newspaper on Sunday printed details of the allegations against Charles, but despite their lurid headlines, most of Britain's press has been restrained from printing more because of legal restraints.
Charles, Queen Elizabeth II's eldest son and heir to the British throne, is due to meet with his son Prince William, companion Camilla Parker Bowles and other royal aides following his return from a 10-day tour of India and the Gulf, The Times newspaper reported.
The latest media frenzy to shake the British monarchy has only intensified since Charles's London residence issued an unprecedented statement last week categorically denying allegations of an incident whose nature can't be revealed in England and Wales because of a court injunction.
Details of the affair have appeared in the press and on the Internet, and on Sunday a Glasgow newspaper became the first to publish them in Britain, exploiting the fact that Scotland enjoys a separate legal system.
"We were aware when we issued the statement denying these ludicrous allegations that there was a possibility that the story would be published in Scotland," The Times quoted a spokesman for Charles' London residence Clarence House as saying.
Some details emerged in the mass-circulation Mail on Sunday which quoted a former royal servant, George Smith, as saying he had witnessed an incident involving Charles and another royal aide.
In another twist to the saga, it was also reported Sunday that a senior aide to Charles once questioned his sexuality.
The scandal overshadowed what should have been happy royal news - the successful birth by emergency caesarean of the first child of Prince Edward, Charles' youngest brother, and his wife Countess Sophie Wessex.
The allegations about Charles came after a week which began with former royal aide Michael Fawcett taking out an injunction against the Mail on Sunday, gagging it from publishing a story based on claims by Smith.
Second-in-line to throne Prince
William (R) remains supportive
Smith was quoted by the Mail on Sunday a year ago as saying he told the late Princess Diana, Charles' ex-wife, in 1996 that he was raped several years earlier by one of Charles' aides.
The News of the World said Charles was planning to take part in "a full-scale" television interview to defend his reputation if full details of the allegations were published.
Britain's newspapers heaped scorn on the royals' handling of the saga. Some of the more unforgiving tabloids have previously claimed that the allegation is powerful enough to bring down the monarchy should it be disclosed.
The furore comes as the monarchy is still reeling from the publication of memoirs by the former royal servant Paul Burrell, one-time butler and confidant to Princess Diana.
The most sensational claim by Burrell was that he had received a letter from Diana 10 months before her death in a Paris car crash in 1997 saying she believed there was a plot to kill her.