An inquiry launched in the wake of the phone-hacking scandal has heard details suggesting that the illegal practice was widespread.

Notebooks belonging to private detective Glenn Mulcaire suggest he hacked phones for the Sun, the Daily Mirror and the News of the World.

Some 28 NoW employees were named in the notebooks, the inquiry heard.

Earlier, Lord Leveson warned newspapers not to victimise inquiry witnesses who speak out against press intrusion.

But he added he had “absolutely no wish to stifle freedom of speech and expression”.

Counsel to the inquiry, Robert Jay QC, gave details of notebooks belonging to Mulcaire, who was jailed with the News of the World’s former royal editor Clive Goodman in 2007 after admitting intercepting messages on royal phones.

Mulcaire wrote first names in the top left-hand corner of his notes recording voicemails he illegally intercepted, the hearing learned.

Some of these corresponded to NoW employees, one of whom – referred to only as “A” – apparently made 1,453 separate requests for information.

But he also wrote “The Sun” and a name relating to the Daily Mirror in his notebooks, the inquiry was told.

About 28 corner names are legible in the 11,000 pages of notes seized by police from Mulcaire, which relate to a total of 2,266 instructions and the names of 5,795 potential victims, the inquiry heard.

Mr Jay said it was clear that hacking was not limited to a single “rogue reporter,” the defence previously mounted by News International, publishers of the now closed NoW.

He said: “I suggest that it would not be unfair to comment that it was at the very least a thriving cottage industry.”

The inquiry heard that actor Jude Law has brought a claim against the Sun for allegedly hacking his phone.

“Part of the evidential matrix in support of his case is a corner name in the Mulcaire notebook which simply states ‘the Sun’ without specifying the individual working there,” Mr Jay said.

The barrister added: “There is also documentary evidence which we have seen of another corner name relating to the Mirror.”

BBC political correspondent Ross Hawkins, who is reporting on the inquiry via twitter, says that Mr Jay has stated that “questions must be asked as to how high up in News International the metaphorical buck stops”.

Responding to the suggestion that Mulcaire may have hacked phones for the Mirror, a Trinity Mirror spokesman said: “The company has no knowledge of ever using Glenn Mulcaire.”

‘More convincing teeth’

Mr Jay also questioned whether the public and politicians had lost faith in the Press Complaints Commission, saying it mainly operated by seeking to find middle ground because it needed to retain the support of the press for what it does.

He said: “The PCC cannot require a newspaper to print a correction or apology on the same page as the original offending article. It can advise and recommend but there is no sanction for disobeying its rulings. Nor has the PCC power to fine newspapers or order them to pay compensation.

“All of this gives the impression that the PCC is operating largely without teeth, and that in the occasionally ruthless world in which it is forced to operate, something altogether sharper is required.”

Meanwhile, Justice Secretary Kenneth Clarke has told the Society of Editors’ annual conference the press watchdog must cover the entire industry if it is to restore confidence following the phone-hacking scandal.

He said he backed self-regulation of the press, adding that newspapers must be allowed “to carry on enraging some politicians, getting under the skin of governments, and deeply embarrassing public figures” where there was a public interest.

Hearings will later examine the extent of unlawful conduct by the press, and the police’s initial hacking investigation.

This second phase will wait until after the current police investigation into NoW phone hacking, and any resultant prosecutions.