Journalists from the News of the World tabloid misled police after hacking the mobile phone of murdered schoolgirl Milly Dowler, action which sparked a scandal engulfing News Corp, a letter from police published on Monday said.
Surrey Police said reporters had lied to police after hacking into Dowler's voicemail messages in 2002 and put pressure on detectives working on her case.
The paper, part of News International, the British arm of Rupert Murdoch's media empire, had demanded answers after claiming it had information Dowler had contacted a recruitment agency, the force said.
One of its reporters had claimed the tabloid had got Dowler's mobile phone details from school children, while the letter discloses someone had called the agency pretending to be Dowler's mother.
It later emerged a message from the agency had mistakenly been left on Dowler's phone because they had the wrong number on their files.
The force dismissed speculation that information published by the News of the World (NOTW) had come from collusion between detectives and the paper.
The NOTW obtained that information by accessing Milly Dowler's phone, Surrey's Assistant Chief Constable Jerry Kirkby wrote in a letter to lawmakers investigating phone-hacking.
It was the revelation by the Guardian newspaper last July that the tabloid's reporters had illegally accessed the voicemail of missing Dowler, who was later found murdered, which caused the phone-hacking to hit the headlines amid widespread public revulsion.
News Corp took the drastic step of shutting down the 168-year-old paper, pulled its plan to take full control of Britain's highly profitable satellite broadcaster BSkyB and Murdoch also personally donated 1 million pounds ($1.6 million) to charities nominated by the Dowler family.
News International also paid the family a further 2 million pounds for behaviour Murdoch described as abhorrent.
The interception of Milly Dowler's phone was shocking and totally unacceptable, a News International spokeswoman said on Tuesday.
The abhorrent nature of what was discovered to have happened at the News of the World ultimately led to its closure last year, she added.
In a twist to the Dowler story last December, police said there was no evidence about a central claim in the original Guardian story that News of the World journalists had deleted voicemails, which had given her parents false hope she was still alive.
An inquiry set up by Prime Minister David Cameron into newspaper practices in the wake of the furore heard that the most likely explanation was that the voicemails had been automatically removed after a 72-hour limit.
The letter from Surrey Police to parliament's Culture, Media, and Sport Committee made no reference to this or why the police had not taken action earlier if it knew her phone had been hacked by the paper.
Instead, Kirkby merely provided details of police dealings with the News of the World in early 2002 during the search for teenager Dowler.
Murdoch's News International had claimed for years that the hacking of voicemails to generate stories was limited to a single rogue reporter who went to jail for the crime in 2007.
Surrey Police have not explained why they did not investigate that deception in 2002, Mark Lewis, the Dowler family lawyer said. No thought seems to have been given to the effect on the Dowler family.
Names of those on the paper involved were redacted as London police are conducting three criminal investigations into phone-hacking, but the letter implied several reporters could have been involved.
Kirkby said his letter detailed Surrey Police's present understanding and a full internal probe into the hacking of Dowler's phone was not yet complete.
Last Thursday, News International settled a string of legal claims from 36 people including celebrities and politicians over phone-hacking, although it said the payouts were not an admission its management knew about the practice or covered it up.
(Reporting by Michael Holden; editing by Keith Weir and Tim Castle)