Sunday newspaper reports said Oliver Hoare, an art dealer, had received silent calls to his home in Chelsea, west London, for more than a year.
Buckingham Palace declined to comment. A spokeswoman said: 'Phone calls of this kind are a matter for the police to investigate and comment on.' A Scotland Yard spokesman said he was not prepared to discuss any aspect of the case.
The News of the World said Mr Hoare, 48, a friend of the Prince and Princess of Wales, had alerted police when he received the silent calls. As a dealer in Islamic art he allegedly feared a terrorist threat.
The calls began in September 1992 but he did not report them until October 1993. Police are reported to have tracked the calls to the princess's private lines at Kensington Palace, a mobile phone she used and the home of her sister, Lady Sarah McCorquodale. Calls were also made from telephone boxes in Notting Hill and Kensington, and a private number in Kensington Palace used by the Prince of Wales.
Mr Hoare is said to have withdrawn his complaint after being told the source of the calls.
A close friend of the princess told the newspaper that the calls had been made by the princess's staff after she had been reduced to tears by Mr Hoare who was acting as self-appointed middleman to try to heal the rift between her and Prince Charles.
However, Piers Morgan, editor of the News of the World, said: 'The News of the World stands by our version of events 100 per cent and we believe Princess Diana made the telephone calls.'
Mr Hoare, who was unavailable for comment yesterday, is believed to have first met the princess 10 years ago. His wife, Diane, is the daughter of Baroness Louise de Waldner, a close friend of the Queen Mother.