"Thousands" of celebrities and politicians were allegedly targeted
The newspaper group News International has been accused of a "cover-up" over claims that its journalists hacked into the mobile phones of public figures.
Giving evidence to MPs, Nick Davies, the Guardian reporter who broke the original story, produced two documents he says back up his allegations.
Mr Davies also told MPs that the Met Police has done too little in the wake of claims about the News of the World.
However, the tabloid denies the practice was widespread.
Mr Davies told the Commons culture, media and sports committee: "News International have been involved in covering up their journalists' involvement with private investigators who are breaking the law.
"And it's very worrying that Scotland Yard do not appear to have always said or done as much as they could have done to stop that cover-up."
Mr Davies said that the former editor of the News of the World, Andy Coulson - now the Conservative Party's director of communications - was not on a list of 31 journalists (27 from the News of the World and four from The Sun) involved in attempts to obtain the personal information of public figures.
Earlier, the Director of the Press Complaints Commission Tim Toulmin said there was no evidence linking Mr Coulson to crimes committed by Clive Goodman, the News of the World's former royal editor, and a private investigator, Glen Mulcaire.
But Mr Toulmin said that the buck stopped with the editor and everyone accepted that it was a "serious oversight" that Mr Coulson did not know what was going on.
Mr Toulmin told MPs there was no proof such practices were currently taking place.
But the PCC would study whether it was "misled into believing that it was more of a contained problem".
The News of the World has rejected claims its reporters regularly hack into the phones of celebrities and politicians to get stories.
The newspaper's owner, News International, accused the Guardian - which claimed up to 3,000 high-profile figures were targeted - of being "selective and misleading".
Assistant Met Police Commissioner John Yates has said "no further investigation" would be conducted into the allegations.
Questioned by members of the home affairs select committee, Home Secretary Alan Johnson said the allegations were an "operational matter" which were being looked at by the director of public prosecutions.