BBC Newsnight has obtained a dossier of evidence from an ex-policeman hired by the News of The World (NoW) which shows the newspaper was engaged in covert surveillance on an industrial scale.
Over eight years Derek Webb was paid to follow more than 90 targets selected by staff at the newspaper.
His targets included Prince William, former attorney general Lord Goldsmith and football pundit Gary Lineker.
Relatives, such as the parents of actor Daniel Radcliffe, were also targeted.
Speaking exclusively to Newsnight's Richard Watson, Mr Webb said that shortly after setting up his own private detective agency in 2003 he was contacted by the NoW and offered work.
He continued to work for the newspaper until it was shut down in July after a string of allegations emerged about the hacking of phones, including that of murdered schoolgirl Milly Dowler.
"I was working for them extensively on many jobs throughout that time. I never knew when I was going to be required. They phoned me up by the day or by the night... It could be anywhere in the country."
