Britain's biggest newspaper group faces a second investigation by Scotland Yard, in addition to the deepening inquiry into phone hacking.
The Metropolitan Police is actively considering launching an inquiry into whether News International journalists made illegal payments to officers.
Disclosure of the move by Cressida Dick, Assistant Commissioner of the Met, came as a judge paved the way for the courts to hear several civil cases brought by public figures against the group's top-selling title, the News of the World, for alleged hacking.
The police also revealed that the number of potential hacking victims by the paper's private investigator Glenn Mulcaire was "substantially higher" than previously thought by detectives, and said they had been "flooded" with enquiries from individuals wondering whether their voicemails had been eavesdropped.
Raising the prospect of a second potentially damaging inquiry, the Yard said it was taking a serious interest into remarks by News International's chief executive Rebekah Brooks to the Commons' Culture, Media and Sport Committee in 2003. Responding to a question from Labour MP Chris Bryant about whether the NOTW, which she edited from 2000 to 2003 had ever given officers money for a story, Ms Brooks said then: "We have paid the police for information in the past."
In a renewed focus on her remarks in the wake of the hacking scandal, MPs have demanded Ms Brooks detail any payments. In a letter to the Home Affairs Committee this week, she sidestepped the issue, saying she had not meant to give the impression she knew about "any specific cases".
In a letter published yesterday, Ms Dick told the committee that another senior officer was looking into the Met's response to Ms Brooks' comments. Deputy Assistant Commissioner Mark Simmons, she said, was conducting "a scoping exercise to establish whether there are now any grounds for beginning a criminal investigation resulting from the comments made by Rebekah Brooks".
Rupert Murdoch's News International last week expressed sincere regret about the hacking scandal, admitted failings in its previous internal inquiries and offered to compensate victims with "justifiable cases". Twenty-four public figures, including the comedian Steve Coogan and jockey Kieren Fallon, are suing the paper.
At a civil case conference at the High Court in London, Mr Justice Geoffrey Vos said he wanted to see up to five test cases put before the courts to clarify how the NOTW and Mr Mulcaire went about hacking and the scale of the damages that should be awarded to victims.
The court heard the four most likely test cases were those of sports agent Sky Andrew, actress Sienna Miller, interior designer Kelly Hoppen and football pundit Andy Gray, with the possible addition of a "political" case such as that of MP Tessa Jowell.
The Met's lawyers told the court that detectives leading the new police investigation into phone message interception had found evidence that showed Mr Mulcaire targeted more individuals than the 91 people whose voicemail PIN codes had been found in his records. Jason Beer QC disclosed that documentation seized from Mr Mulcaire's house in 2006 comprised 9,200 pages. Among these the presence of direct dial numbers – which can be used to access voicemail messages – was being interpreted as being "strongly indicative" that an individual's messages had been accessed by the private detective, he said.
Scotland Yard has been strongly criticised for the failure of its original investigation to inform all potential victims of phone hacking. It claimed there were "only a handful" of cases where interception could be proved.
News International declined to comment on Ms Dick's letter, but said of the test cases: "We made clear last week that our intention was to apologise and to deal with these cases in the most fair and efficient way possible. We believe the judge's recommendations support that."