Cameron told Parliament he has accepted "significant amendments" to the investigation into allegations of phone hacking of public and private citizens by the now-folded News of the World, a property of media mogul Rupert Murdoch, the BBC reported Wednesday.
Besides examining the conduct of individuals in the police, media and politics, the expanded investigation will look into the role broadcasters and social media played.
Cameron returned early from a trip to Africa to take part in an emergency debate on confidence in the media and the police, rattled by the allegations against News of the World and resignations of two senior London Metropolitan Police officers because of the incident. At least nine people, including two former News of the World editors, have been arrested.
A report issued Wednesday said there were "deliberate attempts by News International [Murdoch's British unit] to thwart the various investigations" into the illicit hacking, The New York Times reported. During a House of Commons hearing Tuesday, both Murdoch and son James Murdoch denied they knew of the hacking when it happened.
In his testimony given to the House of Commons media committee, the elder Murdoch said he learned that phone hacking was more widespread at the paper than originally claimed when the company handed information over to the police earlier this year.
Culture Secretary Jeremy Hunt said Murdoch's News Corp. still had to answer questions about why Murdoch and other executives did not know about the extent of phone hacking at the News of the World.
Hunt told the BBC he was "shocked" that "people at the top" did not know about the apparent wrongdoing.
A protester accused of tossing a paper plate of shaving foam at Murdoch during his testimony was charged with a public-order offense, police said.