Investigators inside Scotland Yard are trying to identify up to five officers who were paid between them a total of at least £100,000 in cash from the News of the World, the Guardian understands.
News that officers were allegedly paid so much in bribes has caused shock and concern within Scotland Yard, where the directorate of professional standards is now investigating the matter. There have been calls for an external force to be brought in to investigate the scandal – Boris Johnson, the mayor of London, has said someone else should wash the Met's dirty linen in public.
After concerns were raised that the Met was being left to investigate itself, the Independent Police Complaints Commission (IPCC) announced on Thursday it would be overseeing the initial Met inquiry and could take over the investigation later once the names of the officers had been established.
The IPCC had wanted to hold back until the Met had identified the officers involved, but the growing pressure for an external authority to be involved led to Deborah Glass, deputy chair of the IPCC, announcing she would be personally overseeing the Met's inquiry. The amounts of money involved are likely to have forced the IPCC's hand to get involved sooner rather than later.
The Guardian understands three to five police officers, who are not of senior rank but include detectives, will be the focus of the inquiry. Documents sent to the police on 20 June by News International did not give many clues as to the identity of those who reportedly received payments for information. All the payments are understood to have taken place in 2003, the year Rebekah Brooks handed editorship of the News of the World to Andy Coulson.
Glass, who as well as being IPCC deputy chair also has oversight for the Met, said: "I share the public concerns expressed so powerfully about police officers being bribed by newspapers. It is obviously crucial that the officers involved are identified. I will personally supervise this investigation to give independent oversight and ensure that it is robust in its attempts to identify any officer who may have committed an offence."
Once those officers had been identified, she said, the IPCC "will review our level of involvement so that we can exercise our full range of powers".
"Public confidence has been understandably shaken by these allegations," Glass said. "By providing independent oversight I want to be able to be satisfied and say with confidence to the public that the Met has done everything it can to identify the officers involved."
The Met commissioner has said that anyone who is shown to have committed any wrongdoing can expect the full weight of disciplinary measures, if appropriate through the criminal courts.
When asked how he felt about those suspected of taking money, he told Sky News: "I am more than ashamed – I am determined to see them in a criminal court."
There have been calls for an independent police force to be brought in immediately to investigate the illegal payments. Joanne McCartney, a member of the Metropolitan police authority, has said there is a "lot of disquiet" that the police are being left to investigate themselves and called for an external force to be brought in.
"I think public confidence has to be restored," she said. McCartney indicated that members of the MPA could tell the force to hand their investigation over to an independent team of officers.
Boris Johnson said on Thursday that the inquiry had to be overseen by an external authority. "There has got to be a strong sense that the investigation into this has got to be independent and the public has got to understand this is not just the Metropolitan police doing its own investigation. This has got to be a validation by an external authority," he said.
This, he added, involved the inquiry into the payments that might have been made to officers and the handling of the original police investigation into phone hacking.
The inquiry is being led by Deputy Assistant Commissioner Sue Akers, along with the force's Directorate of Professional Standards.
Akers said: "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."