Lord Justice Brian Leveson said the inquiry, which will initially look at the culture, practices and ethics of the media and then move into alleged unlawful activities, would look at "who guards the guardians?," The New York Times reported Monday.
The News of the World, operated by the British newspaper arm of Rupert Murdoch's News Corp., was closed in July after it was revealed journalists illegally intercepted voice messages.
Sixteen people have been arrested in the phone hacking inquiry and six people have been arrested in a probe into illegal payments to police officers.
As the hearings opened Monday, an inquiry attorney said the names of 28 employees of The News of the World were found in notebooks belonging to Glenn Mulcaire, the private investigator who worked for the now-defunct newspaper, The Guardian reported.
The phone hacking scandal has raised questions about the relationship between privacy and the press in Britain. The New York Times said Actor Hugh Grant and "Harry Potter" author J.K. Rowling are expected to be among the witnesses to testify about the press' intrusion into their lives.
Wisconsin business offering 'therapeutic cuddling' forced to close
Ukrainian protestors topple Lenin statue [VIDEO]