The late Princess of Wales, who was killed in a car crash in Paris in 1997, regularly changed her mobile after security experts warned her that she was the target of spies, snoopers and phone tappers, the 'Daily Express' reported.
"It was clear that was a concern to her," the British newspaper quoted her former private secretary Michael Gibbins as telling her inquest in 2007.
Not only Diana, her sons Prince William and Prince Harry were also victims of Glenn Mulcaire, a private detective employed by the 'News of the World', Britain's best-selling Sunday tabloid, the report said.
One hacked message is said to have featured William pretending to be his brother's girlfriend, ticking him off for staying out late, the newspaper said.
Mulcaire was jailed in 2007 for hacking into messages for three aides working for the Princes. The Duchess of York is also believed to have been a hacking victim, it added. James Murdoch, the chairman of News International, yesterday announced the closure of the 'News of the World' following a ruckus over its news gathering practices that involved the illegal hacking of phones.