Former policeman says he surveilled figures including Prince William and the parents of Harry Potter actor Daniel Radcliffe

A private detective has claimed that the News of the World paid him to target more than 90 people, including Prince William, former attorney general Lord Goldsmith and Harry Potter actor Daniel Radcliffe's parents, over eight years until this July.

Derek Webb, a former police officer, said he started work for the paper shortly after setting up his private detective agency in 2003. He told the BBC's Newsnight he continued to do surveillance until it was closed over the phone-hacking scandal.

The investigator said he was paid by the paper to follow more than 90 targets including Prince William, Goldsmith, Radcliffe's parents and Match of the Day presenter Gary Lineker.

"I was working for them extensively on many jobs throughout that time. I never knew when I was going to be required. They phone me up by the day or by the night … it could be anywhere in the country," Webb told Newsnight's Richard Watson, in a report broadcast on the BBC2 daily current affairs show on Tuesday night.

In 2006 he was asked to follow Prince William while he spent a few days in Gloucestershire.

Webb did many years on covert surveillance and had MI5 training. He told the BBC he set up his own detective agency in 2003 and was approached shortly after that by the News of the World.

Most commissions were by phone, but sometimes he was sent photos or addresses; orders came from several NoW journalists, he reveals.

The Guardian revealed yesterday that the News International title had also paid Webb to run covert surveillance on two lawyers representing phone-hacking victims in an operation to pressure them to stop their work. Webb secretly videoed Mark Lewis and Charlotte Harris as well as family members and associates.

Evidence suggests an attempt to gather evidence for false smears about their private lives. Others named in the programme are former Chelsea manager José Mourinho and Prince Harry's ex-girlfriend Chelsy Davy. His targets rarely suspected: "95% of the job, I was never rumbled, even following them for weeks on end."

He said what he did was not illegal and he had decided to speak out after the News of the World failed to compensate him in July. Its former features editor Jules Stenson told Newsnight Webb's story was "one-sided", "very slanted" and the view of a man with "a grievance" due to an issue of payment.

Stenson's appearance on Newsnight was almost as significant as Webb's, as few top journalists have come out to defend the paper. He said he was "extremely surprised" by this week's news that the paper hired Webb to follow the two lawyers.