Legal letters sent by the News of the World to detectives have cast doubt on News International's repeated claims that the company co-operated fully with the police inquiry into phone hacking.
In the letters, which have been seen by the Guardian, the Murdoch-controlled tabloid states that "extensive searches" had been carried out but the company could find only a single piece of paper covering the years of work by the private investigator Glenn Mulcaire.
Detectives who began investigating in 2006 the extent of phone hacking at the paper wrote to News International to ask for information about "co-conspirators" of Mulcaire and the NoW reporter Clive Goodman. They were pressing for information on who Mulcaire had worked for, and to whom he had provided information.
Scotland Yard were investigating Mulcaire and the paper's royal editor Clive Goodman for phone hacking and had written to the NoW asking for information and details as they tried to identify "all persons that may be involved including and fellow conspirators".
Publicly top NI executives have claimed at appearances in front of MPs to have co-operated fully with police.
But the letters from NI's lawyers to police challenge those assertions.
It was only years later that the company handed over other material to police suggesting phone hacking was wider than just one rogue reporter.
The revelations come as James Murdoch is under pressure over his knowledge of a document which appears to show that another reporter, Neville Thurlbeck, below, had knowledge of the practice.
Murdoch claimed before MPs not to have known about that document, only for two former NI executives to contradict him on Thursday. He says he stands by his evidence to MPs. On Wednesday, an all-party group of MPs on the home affairs committee found that NI had "deliberately" tried to "thwart" justice.
According to the letters that have now come to light, by August 2006, NI had produced and handed over to police paperwork covering payments to Mulcaire.
On 31 August 2006, BCL Burton Copeland, lawyers for the paper's owners, said: "My clients intends to provide such material as you … might reasonably require from them in connection with your inquiries."
On 7 September 2006, police wrote back. A detective asked for more information as police decided to identify "co-conspirators" involved in phone hacking.
The Metropolitan police wrote: "Who does Mr Mulcaire work for? Has he completed work for other editors/journalists at News of the World?
"Can we have a copy of any other records for work completed by Mulcaire for these editors/journalists, including the subjects on whom he might have provided information?"
The detective then explains why the police want this information: "The investigation is attempting to identify all persons that may be involved."
On 14 September 2006, Burton Copeland wrote to a detective sergeant at the Met's anti-terrorism branch which was conducting the investigation, because it is responsible for royal security.
By this time, they said, they had "had an opportunity to take full instructions in relations to the material held by Newsgroup Newspapers Limited", the legal entity that owned the NoW.
The lawyers wrote: "In fact very little documentary or other material in relation to Mr Mulcaire, Nine Consultancy Limited [Mulcaire's company] or Mr Goodman exists. This is entirely consistent with normal business practices in relation to the use of such consultants."
It then said it had sent police all the paperwork it had "relating to the contract of employment" between Mulcaire and the tabloid. "Extensive searches have revealed the existence of only one piece of paper, enclosed herewith.
"No documents exist recording any work completed by Mr Mulcaire, monitoring of Mr Mulcaire's return of work, reporting structures or any persons for whom Mr Mulcaire provided information."
That last statement has proved to be incorrect as the paper had in its possession an agreement to pay a "Paul Williams", a pseudonym used by Mulcaire, for work on Gordon Taylor, the Professional Fooballers' Association chairman. It was signed for the paper by Greg Miskiw.
It went on to say it could not provide an "itemised" breakdown of phone calls from individual extensions. It claimed that "will amount to confidential journalistic material". It said that the company "wishes fully to assist your investigation and does not require any formal court order for the provision of any material.
"They are however entirely satisfied that the material to which you are entitled is limited and that you are now, along with material previously submitted, in possession of all relevant documentation."
Mulcaire received over £100,000 in payments from the paper, some in cash.
Police have said that they were given advice from the Crown Prosecution Service and their own lawyers suggesting they fell short of having grounds for a "production order", requiring material to be handed over.
So they had to write to NI requesting material. The police told MPs the company had carefully crafted letters to ensure detectives could not use them as evidence of obstruction and thus seek a court order compelling the production of material.
Peter Clarke, who oversaw the first investigation, told the home affairs committee earlier this month that he thought NI had tried to obstruct justice.
Clarke said NI's size and wealth to afford the best legal advice had been a factor in his investigation, which he said was also hampered by the law.
Clarke said: "This is a major global organisation with access to the best legal advice, in my view deliberately trying to thwart a police investigation.
"If at any time News International had offered some meaningful co-operation instead of prevarication and what we now know to be lies, we would not be here today."
BCL Burton Copeland said it would not comment on work carried out on behalf of a client. It is usual practice for lawyers to be acting on the instructions of their clients.
Site's plea for NI leaks
Whistleblowers with inside information about malfeasance at News International are being encouraged by a new Wikileaks-style site to submit details about events in the company.
The site, created on 13 July, offers secure, anonymous methods to submit "tips or evidence of wrongdoing relating to Rupert Murdoch's affiliated institutions such as News International and News Corporation. Credible submissions will be distributed to our network of journalists (actual journalists) and law enforcement agencies in the UK, the US and Australia. We will not publish anything ourselves." It adds that "We do not accept rumor, opinion or material that is publicly available elsewhere... Credible submissions will be distributed to our network of journalists... and law enforcement agencies in the UK, the US and Australia. We will not publish anything ourselves." The Guardian does not know who is behind the site and is not collaborating with it.
Spelling on the site, such as the American "rumor" rather than the English "rumour" implies that the author is American. The site is hosted via CloudFlare, a service increasingly popular among hackers seeking to cover their tracks. Charles Arthur