Rebekah Brooks's phone was hacked twice a week by colleagues at the News of the World while she was editing The Sun, the Leveson Inquiry has heard.
Scotland Yard invited her to join their 2006 prosecution of a journalist and private detective working for the Sunday tabloid as a potential victim of illegal interception of voicemails.
Ms Brooks - who was herself a former editor of the News of the World, The Sun's sister paper, and became chief executive of parent company News International in 2009 - did not take up the offer.
She in fact passed on information about the hacking investigation she gleaned from the police to the News of the World's lawyers.
Robert Jay QC, counsel to the press standards inquiry, said today: "Rebekah Wade, as she then was, was one of the most accessed since 2005, twice a week."
Tom Crone, the News of the World's head of legal, summarised the information Ms Brooks received from police in an email headed "strictly private and confidential" to the paper's then-editor Andy Coulson on 15 September 2006.
The memo concluded: "They're going to contact RW (Rebekah Wade, Ms Brooks's maiden name) today to see if she wishes to take it further."
Mr Jay commented: "This relates to a formal complaint that Rebekah Wade might make in her capacity as victim.
"It is not the more sinister interpretation, whether she wishes to take the investigation into News International further."
Detective Chief Superintendent Philip Williams, who led the Metropolitan Police's original investigation into phone-hacking, agreed, saying: "This is purely 'You're a potential victim, would you like to join our prosecution?'"