Rebekah Brooks, the embattled chief executive of Rupert Murdoch's News International, personally commissioned searches by one of the private investigators used by the News of the World (NOTW) to trace the family of the murdered Surrey schoolgirl Milly Dowler, it can be revealed.
Ms Brooks, while editor of NOTW, used Steve Whittamore, a private detective who specialised in obtaining illegal information and provided the paper with the Dowlers' ex-directory home phone number, to "convert" a mobile-phone number to find its registered owner.
The Information Commissioner's Office (ICO), which successfully prosecuted Whittamore for breaches of the Data Protection Act in 2005, said last night it would have been illegal to obtain the mobile conversion if the details had been "blagged" from a phone company.
Ms Brooks, who said yesterday she was "shocked and appalled" at the latest hacking claims, admitted requesting the information. But she said it could be obtained by "perfectly legitimate means". She faced demands for her resignation last night.
The revelation came as News International battled a firestorm over the disclosure that its best-selling paper interfered with the police investigation into Milly's disappearance in March 2002 by hacking into her mobile phone and deleting messages.
David Cameron described the hacking as a "truly dreadful act", but rebuffed the call for a public inquiry. He insisted Scotland Yard be allowed to follow the evidence wherever it led.
Yesterday it led to Cambridgeshire, where police confirmed there was evidence that Glenn Mulcaire, the NOTW's private investigator who is accused of hacking Milly's phone, targeted the families of Holly Wells and Jessica Chapman, who were murdered in Soham in 2002.
Responding to growing clamour for her to step down, Ms Brooks yesterday told News International staff it was "inconceivable" that she knew of or sanctioned the hacking of Milly's mobile phone.
In defence of her position, she wrote: "I have to tell you that I am sickened that these events are alleged to have happened."
No evidence has been presented that Ms Brooks was aware of Mulcaire's activities surrounding Milly's disappearance. But she was aware of the existence of Whittamore, who used an associate to obtain the Dowlers' home phone number from BT, and made use of his services in an unrelated case.
A copy of the 'Blue Book', which covers more than 1,000 transactions carried out for News International's titles between 2000 and 2003, records a request in 2001 from Ms Brooks (who's surname was then Wade) for a "mobile conversion" along with a mobile-phone number.
An ICO spokeswoman said: "If that information was obtained by 'blagging' then it would have been illegal under Section 55 of the Data Protection Act."
Others also suspect they may have fallen victim to Mulcaire.
Clarence Mitchell, spokesman for the parents of Madeleine McCann, said friends of Kate and Gerry McCann may have had their phones hacked after the girl went missing in 2007.
The mother of a six-year-old boy who died after his father threw him from their hotel balcony in Crete may have been another victim. Natasha Hogan's family now intend to contact police.
And the mother of up-and-coming model Sally Anne Bowman (18), who was murdered in 2005, said news that Milly Dowler's phone had been hacked added to her suspicions that her daughter's mobile had been targeted after she was killed.
As the fallout from the row continued, Mulcaire, whose home was besieged by reporters, said he had been acting under "relentless pressure" from the paper.
News International spokesman Simon Greenberg said the company had launched a full inquiry into the hacking of Milly's phone during Brooks' editorship.
David Cameron will today come under intense pressure to give way and order a full public inquiry into telephone hacking by the News of World after the Commons Speaker ordered an emergency debate into the scandal. The three-hour debate scheduled for this afternoon could also lead to further damaging allegations about hacking at the paper under the protection of parliamentary privilege.