One or more News of the World journalists deleted voicemails from murdered teenager Milly Dowler's mobile phone, the Leveson Inquiry into press standards has heard.
Guardian journalist Nick Davies said private investigator Glenn Mulcaire was the "facilitator" of the hacking of the schoolgirl's phone by the now-defunct Sunday paper.
He told the inquiry: "Mulcaire facilitated the hacking by one or more News of the World journalists. And our understanding of the facts is that it was one or more of the News of the World journalists who then had to delete the messages in order to enable more to come through."
Mulcaire was jailed along with the News of the World's former royal editor Clive Goodman in January 2007 after they admitted intercepting voicemail messages left on phones belonging to royal aides.
Mr Davies, who revealed the scale of phone hacking at the News of the World in a series of Guardian articles, said Mulcaire's role had been misunderstood.
He told the inquiry: "The facilitator was Glenn Mulcaire. There is a misunderstanding, I think, around the way that he operates. He does not actually, on the whole, do the listening to the messages himself. Most of that is done by the journalists themselves.
"Mulcaire's job was to enable them to do that where there's some problem because he's a brilliant blagger, so he could gather information, data from the mobile phone company. Occasionally, I think, he did special projects - I think perhaps the royal household would be an example."
Earlier, a former Daily Star journalist has claimed that he received threats and may have had his phone hacked after he quit the paper in protest at what he claimed was its anti-Muslim propaganda.
Richard Peppiatt told the Inquiry that he received threatening phone calls, text messages and emails after he leaked his outspoken resignation letter to the Guardian newspaper.
Mr Peppiatt said the messages included, "We're doing a kiss and tell on you", "You're a marked man until the day you die", and "RD will get ya" - a reference, he suggested, to Express Newspapers owner Richard Desmond.