A private detective working for the News of the World is accused of hacking into Milly Dowler's voicemail after she went missing, a lawyer for the murdered schoolgirl's parents has said.
Scotland Yard officers contacted Sally and Bob Dowler about the allegations in April, a month before Levi Bellfield went on trial for her murder, said solicitor Mark Lewis.
Private investigator Glenn Mulcaire is alleged to have illegally accessed Milly's phone messages after she was abducted by Bellfield as she walked home from school in Walton-on-Thames, Surrey, in March 2002.
Mr Lewis, from London-based Taylor Hampton Solicitors, said: "Sally and Bob Dowler have been through so much grief and trauma without further distressing revelations to them regarding the loss of their daughter.
"It is distress heaped upon tragedy to learn that the News of the World had no humanity at such a terrible time.
"The fact that they were prepared to act in such a heinous way that could have jeopardised the police investigation and give them false hope is despicable."
Mr and Mrs Dowler are now pursuing a claim for damages against the News of the World, said Mr Lewis.
Scotland Yard and the News of the World's publishers, News International, declined to comment on the allegations.
Mulcaire and former News of the World royal editor Clive Goodman were given jail terms in January 2007 after the Old Bailey heard they plotted to hack into royal aides' telephone messages.