Sir Alex Ferguson's phone messages were allegedly intercepted
Public figures who believe they were victims of alleged phone hacking by investigators hired by the News of the World are considering suing the paper.
One lawyer told the BBC he has had two enquiries and that more celebrities and politicians were seeking advice.
It follows claims in the Guardian that the tabloid paid £1m to settle legal cases which threatened to expose the use of illegal methods to get stories.
Scotland Yard has said it will not investigate the fresh allegations.
Liberal Democrat home affairs spokesman Chris Huhne has called on the Independent Police Complaints Commission to investigate this decision on the grounds police had reviewed the evidence "too quickly to be thorough".
The IPCC said it had not yet decided whether or not to proceed with an inquiry.
In its latest revelations, the Guardian had named Manchester United manager Sir Alex Ferguson and former England captain Alan Shearer among those whose messages were allegedly intercepted.
Three inquiries have been launched by the director of public prosecutions, the Press Complaints Commission and a Commons select committee.
The Metropolitan Police have already conducted an investigation into phone hacking by journalists at the News of the World, centring on messages left for aides of Prince Charles.
Vanessa Feltz: "I'm shocked, I'm bewildered at what seems to pass for journalism"
It resulted in royal editor Clive Goodman and private investigator Glenn Mulcaire being jailed for four and six months respectively in January 2007.
The scandal led to the resignation of then editor Andy Coulson, who is now the Conservative Party's public relations chief.
The BBC has learned that the News of the World was behind Mulcaire's monitoring of phone messages left for Rebekah Wade, the editor of its sister paper, the Sun.
Ms Wade - soon to become chief executive of the papers' parent company News International - was informed at the time but declined to press charges, according to BBC business editor Robert Peston.
On Thursday, Met Assistant Commissioner John Yates said Scotland Yard would not reopen its files on the case because no new evidence had come to light since its original inquiry.
Robert Peston BBC business editor
For anyone running more-or-less any substantial news organisation, it'll be difficult to know whether to welcome or dread the Guardian's investigation.
Some will see it as an incentive for journalists to clean up the way they carry out investigations.
Others will fear it will restrict the ability of journalists to uncover genuine wrongdoing.
But over-riding all other thought and emotions will be one terrifying question: "Is my news organisation going to be seriously tainted by this?"
Because more-or-less every newspaper employed journalists whose specific skill was to obtain... confidential personal information.
And these specialist hacks in turn got hold of the valuable data through their relationships with private investigators.
He said Goodman and Mulcaire had undertaken a "sophisticated and wide-ranging conspiracy to gather private and personal data".
He added the inquiry had focused solely on phone hacking, and in the vast majority of cases, there was "insufficient evidence" that interception had happened.
Mark Stephens, of law firm Finers Stephens Innocent, said Mr Yates' statement seemed "not to address the possibility that there had been a criminal attempt or criminal conspiracy".
He said the director of public prosecutions, Keir Starmer QC, could force police to reopen the investigation or order the release of documents "sealed" by civil courts under case confidentially agreements.
This could shed light on whether other high-profile figures had been phone hacking victims, he added.
One former Met deputy assistant commissioner, Brian Paddick, suggested Mr Yates may not have spent enough time reviewing the evidence.
He also said the Royal Protection Officers who investigated the Goodman case may not have passed on evidence of hacking affecting figures outside the Royal Family to other sections of the force for a wider investigation.
Mr Starmer has said he wants to reassure himself and the public that "appropriate actions" were taken by the police three years ago.
"Given the nature of the offences, the amount of material is, of course, extensive and complex, but it has all been located and a small team is now rapidly working through it," he said.
The Commons culture, media and sport select committee has announced it will reopen an inquiry held after Goodman was jailed and may call Mr Coulson to give evidence.
Mark Stephens: "I've had two clients contact me about pursuing legal action"
During the Goodman trial, it emerged Mulcaire had hacked into the phones of model Elle Macpherson, publicist Max Clifford, Simon Hughes MP and the Professional Footballers' Association's chief executive Gordon Taylor.
Mr Taylor later sued News Group, which owns the News of the World, receiving £700,000 on condition that the case details remained confidential.
During this case, the Guardian claims, details emerged that "two or three thousand" figures had been targeted.
News International, the parent company of News Group, said it would be "inappropriate" to comment on the Guardian's allegations.
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