Police reveal there are 4,000 possible victims of phone hacking as the IPCC tells Channel 4 News it may move to take full control of an inquiry into alleged payments by journalists to Met officers.
The true scale of the scandal - engulfing News International, the police and the Government - has been revealed by Met Police Deputy Assistant Commissioner Sue Akers who said her investigators are "going through approximately 11,000 pages of material".
It comes as the UK's police watchdog steps in to oversee investigations into claims Scotland Yard officers illegally received large sums of money from the News of the World, which is being shut down after Sunday's final edition.
The Independent Police Complaints Commission (IPCC) will supervise Operation Elveden, an internal inquiry announced by Met Police Commissioner Sir Paul Stephenson who has said, if the claims prove accurate, he is "more than ashamed".
I want to see anyone who engages in corrupt practises, any criminality in my organisation where they belong - and it's not in uniform. Sir Paul Stephenson
A spokeswoman for the IPCC told Channel 4 News it may yet take full independent control of the investigation once the accused officers have been identified. She said she "could not rule out" such a move.
It is alleged police may have received up to £100,000 in bribes from journalists and senior executives at the newspaper at the centre of the phone hacking scandal. Former deputy assistant commissioner Brian Paddick said on Thursday that individual officers could have been paid as much as £30,000 in return for information.
Sir Paul told reporters: "I want to see anyone who engages in corrupt practises, any criminality in my organisation where they belong - and it's not in uniform."
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Police confirmed on Wednesday that documents were handed to them on 20 June by News International, the News of the World's parent company, which "include information relating to alleged inappropriate payments to a small number of MPS officers".
The referral to the IPCC was made in the light of the significant public and political concern expressed following recent revelations, the Met Police said.
Dept Asst Commissioner Sue Akers explained: "We recognised the gravity of this case from the outset and involved the IPCC at the first opportunity.
"I strongly believe in and welcome independent oversight, especially in a case such as this, where public confidence in the police is seriously at risk."
Akers is leading the wider investigation into phone-hacking, Operation Weeting, which is being carried out by at least 45 officers, making it the biggest non-murder inquiry in police history.
It is this team that is wading through 11,000 pages of material which Dept Asst Comissioner Akers has confirmed contains 4,000 names. She said: "We have contacted many people already and will contact others whose details appear as quickly as possible.
We have contacted many people already and will contact others whose details appear as quickly as possible. Deputy Assistant Commissioner Sue Akers
"We are also making contact with organisations that represent the large groups of people reported to be affected to provide reassurance."
A Met police spokesman told Channel 4 News the force is "reviewing" the way people can contact police but said it is not yet considering setting up a dedicated emergency phone line.
Until now it has been high profile names and celebrities in the hacking spotlight. In June, actress Sienna Miller accepted £100,000 in damages over her case.
But in recent days it has been alleged the families of murder victims, including Milly Dowler and the Soham schoolgirls, were hacked as well as relatives of soldiers serving in Afghanistan and the families of people killed in the 7/7 terrorist attacks in London.
The Met has been widely criticised for the narrow scope of its original investigation into the hacking scandal in 2005-06. Officers restricted their inquiries to a single journalist and did not interview the paper's bosses.
In 2007, NoW's former royal editor Clive Goodman and private investigator Glenn Mulcaire were jailed for intercepting voicemail messages of the Royal family.
It is the contents of Mr Mulcaire's detailed notebooks, in the possession of police since 2006, that are at the centre of the current investigation.
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Prime Minister David Cameron has indicated there could be one all-encompassing inquiry into the whole affair, or there could be two - one into the police handling of the original hacking investigation, and one into the actions of the media. Mr Cameron hired former News of the World editor Andy Coulson as his communications chief in 2007. Coulson was forced to quit in January because of the phone hacking furore.
London Mayor Boris Johnson has said he is open to the idea of another UK police force moving in on the case. He told BBC Radio 4 there should be "external validation" of the Metropolitan Police's inquiry into its own handling of the case, adding: "There has to be confidence that this is not just the police washing their dirty linen."
Reports are circulating a further five journalists and newspaper executives will be arrested within days.