The mother of the murdered schoolgirl Sarah Payne was left "absolutely devastated" after being told by police that her phone may have been hacked by a private investigator used by the News of the World, a friend has said.
Sara Payne, who worked closely with the Sunday paper to campaign for tougher child protection laws, previously said she had not been told she was a victim of phone hacking.
But her friend Shy Keenan has now confirmed that Scotland Yard has since informed her that her contact details were found on a list compiled by private detective Glenn Mulcaire.
Former News of the World editor Rebekah Brooks, who became close friends with Ms Payne during the paper's campaign, said the latest allegations were "abhorrent".
It is believed that the evidence found in Mulcaire's files relates to a phone given to Ms Payne by the News of the World so she could contact her supporters, the Guardian reported.
Ms Brooks said in a statement: "For the benefit of the campaign for Sarah's Law, the News of the World have provided Sara with a mobile telephone for the last 11 years. It was not a personal gift. The idea that anyone on the newspaper knew that Sara or the campaign team were targeted by Mr Mulcaire is unthinkable. The idea of her being targeted is beyond my comprehension. It is imperative for Sara and the other victims of crime that these allegations are investigated and those culpable brought to justice."
A source close to News of the World staff said it is understood that Ms Payne's phone did not have voicemail until 18 months ago.
Ms Payne was "deeply disappointed" when the news was broken to her by officers, her child welfare group The Phoenix Chief Advocates said.
Ms Payne wrote a column for the final issue of the News of the World on July 10 after it was closed amid the phone hacking scandal, and in it she described the paper and its staff as "an old friend" and told how it became a driving force behind her campaign for a "Sarah's law" to give parents the right to find out if people with access to their children are sex offenders.
A News International spokesman said: "News International takes this matter very seriously and is deeply concerned, like everyone. As the facts are established, the company and the independent Management and Standards Committee will take all appropriate actions, including co-operating fully with any potential criminal inquiries or civil proceedings which may arise."