Surrey Police failed to follow-up indications that the News of the World hacked murder victim Milly Dowler's phone, new documents released by MPs appear to show.
The detailed reports of exchanges between police and the former Sunday tabloid were released by the Department of Culture, Media and Sport select committee on Monday.
They show that a News of the World journalist told police they obtained Milly Dowler's mobile phone number and pin from schoolchildren.
The documents then detail frantic discussions between the Surrey Police and a story the NotW was preparing to run on 13 April 2002, that a recruitment agency in the West Mercia constabulary had contacted Milly Dowler.
They show that the News of the World told Surrey Police in 2002 that it had obtained Dowler's mobile number and voicemail pin code.
Staff at the agency arrived at work to find "hordes of reporters from the News of the World waiting for their arrival as if they had been given the same info", the documents say.
Reporters from the paper claimed to be working with the police, which was untrue, the documents claim.
The confusion arose after a woman claiming to be Dowler approached them for work, leaving Dowler's number. The woman had called the number and left a voicemail inviting her for an interview.
According to the documents the police were told that the News of the World was in possession of a recording of that voicemail message.
The letter says that on April 13 2002, "the press officer spoke to (name redacted) and asked him why he was so convinced that the message on Milly's voicemail was not a hoax", the letter said.
An unnamed representative from the tabloid is said to have played police a recording of a voicemail left by the recruitment agency.
The NotW told police Dowler's friends had given them the number as well as her PIN code.
The documents say that NotW "played the Surrey Police press officer a recording of the message left by the recruitment agency on Milly's voicemail".
"The press officer stated that the name of the person seeking employment was 'Nana'," the document said.
"The press officer said that there were a number of people on the recruitment agency's books from Ghana, and that the call from the recruitment agency was intended for one of them.
"(Name redacted) responded by saying that what the Surrey Police press officer was saying was inconceivable. (They) said that there were other messages on Milly Dowler's phone (e.g. a message saying 'It is America, take it or leave it'."
The NotW also informed police that they knew of voicemails from "a tearful relative" and a "young boy".
Conservative MP Damian Collins, a member of the select committee, writes today in a blog for the Huffington Post UK:
"Of all of the documents and evidence that have been produced by our phone hacking inquiry, this is the most sickening and exposes the black hearts of those involved in perpetrating and covering up this scandal.
"When Rebekah Brooks gave evidence to our committee in July 2011 I asked her whether she was aware that the News Of The World had passed messages hacked from Milly Dowler's phone to the Surrey Police.
"She said that she had only become aware of the allegation that Milly's phone had been hacked two weeks previously, and had no knowledge of information having passed on to the Surrey Police in 2002.
"As I said to Rebekah Brooks at the time, I think it is incredible that that could have happened without the knowledge of senior people on the paper."
Mark Lewis, the lawyer who works for Milly Dowler's family as well as dozens of other hacking victims, said in a statement on behalf of the Dowlers:
“The release of the Surrey Police statement is a further reminder of the relationship between that force and the News of the World. Current investigations are ongoing as to the propriety of that relationship.
"The report indicates that the police force were aware of a caller purporting to be Sally Dowler seeking information in 2002. No doubt there will be current investigations as to who that was as it was not Sally Dowler. The Surrey Police have not explained why they did not investigate that deception in 2002.
"No thought seems to have been given to the effect on the Dowler family. The family await the investigation by Lord Justice Leveson about the relationship between Police forces and the press. The Dowler family would be grateful if they could now be left alone”
Keith Vaz, chairman of the Commons Home Affairs Committee - which has also probed phone hacking - said: "The information provided by Surrey Police raises serious questions over what they knew about phone hacking and when.
"Had they acted in 2002 or had Sussex Police flagged this up in their review of Operation Ruby, it may have prevented the culture of hacking becoming endemic at News of the World.
"The Home Affairs Committee has also received a letter from Surrey Police with additional information to questions posed back in October 2011. We will be considering this information carefully and will look into investigating the reasons why Surrey Police did not follow up on this evidence."
The Guardian reported last July that the NotW hacked Milly's mobile and erased messages shortly after her disappearance in March 2002.
However, the Metropolitan Police have since indicated that, while reporters did access voicemails, they are unlikely to have been responsible for the deletions which gave the family false hope.
Instead the recordings may have been automatically removed by the phone company after being listened to.
The Surrey Police letter timetable published today - dated 17 January 2012 - does not shed any further light on that issue.
It also dismisses the idea that the force was the source of the tabloid's stories, and said there was "no evidence" of any discussions about voicemail evidence after April 20 2002.
The timeline raises fresh questions about the way detectives conducted the original investigation, and whether they could have been inadvertently responsible for triggering the deletion of voicemails.
Surrey Police first obtained an evidence Production Order and accessed Milly's voicemails on 26 March, finding one message, according to the document.
But it was not until 17 April that the force secured a second Order and downloaded further messages, including that left by the recruitment agency.