The Guardian claimed thousands were targeted by the News of the World
Allegations of widespread phone-tapping at the News of the World have been rejected by the press watchdog.
In July, the Guardian reported claims that numerous public figures may have had their messages hacked into.
But after investigating, the Press Complaints Commission (PCC) said it had found "no evidence" that phone-message tapping was still going on.
The News of the World said it would not be commenting. But the Guardian called the PCC's findings "complacent".
In 2007, the News of the World's royal editor Clive Goodman and associate Glenn Mulcaire were jailed after admitting hacking into the phone messages of royal staff.
The paper said it was an isolated case.
But a Guardian investigation uncovered evidence that the Sunday paper had paid hundreds of thousands of pounds to settle legal actions with Gordon Taylor, head of the Professional Footballers Association, and others over similar claims.
It also reported allegations that numerous public figures had been targeted.
The Press Complaints Commission said the revelation that Gordon Taylor was paid a large sum was new and "significant", but it found no evidence that tapping into phone messages was ongoing, nor that the News of the World misled it during its previous investigation.
An inquiry by the PCC concluded: "The Commission is satisfied that - so far as it is possible to tell - its work aimed at improving the integrity of undercover journalism has played its part in raising standards in this area."
It said the Guardian was "performing a perfectly legitimate function in further scrutinising activity at the paper", but had uncovered nothing "concrete" to prove there was a "hitherto concealed criminal conspiracy at the News of the World".
The Guardian had said that the phone hacking was far more widespread, affecting "thousands" of celebrities and politicians.
These were said to include former deputy prime minister John Prescott, London Mayor Boris Johnson, former culture secretary Tessa Jowell, actress Gwyneth Paltrow, model Elle Macpherson and publicist Max Clifford.
In a statement, the Guardian said the PCC's inquiry showed that the watchdog "does not have the ability, the budget or the procedures to conduct its own investigations".
It continued: "The report confirms the central allegation made by the Guardian and has not produced any independent evidence of its own to contradict a single fact in our coverage."
The statement added that the PCC had "not spoken to a single person involved in the widespread past practice of phone hacking, limiting its own original inquiries to an exchange of letters with someone who was not even at the News of the World at the time of the hacking".