Nick Davies told the Leveson Inquiry today that around 15 to 20 former News of the World journalists had spoken to him or his researcher about phone hacking at the paper.
Asked about the sources of his hacking revelations published in the Guardian, Davies said the ex-NoW journalists had been a "tremendously important engine driving the story forward".
Davies said other sources included private investigators who were alarmed by "cowboys" in their trade and also the victims of phone hacking and their legal actions.
He told the Leveson Inquiry that some of his sources would only speak off the record if guaranteed anonymity.
Davies argued that an advisory body should be set up that could judge whether potential stories were in the public interest but would not have the power to prevent publication.
He said he didn't think the press was an industry capable of self-regulation and that he was in favour of corrections being given equal prominence to the offending story.
Davies also claimed it was News of the World journalists that deleted Milly Dowler's phone messages and private investigator Glenn Mulcaire who had "facilitated" the hacking.
- Nick Davies' witness statement.