Other tabloids besides Rupert Murdoch's News of the World may have hacked phones, a London court heard on Monday as it began an investigation into newspaper practices that could lead to tougher regulation of the entire UK press.
The Leveson inquiry, expected to take about a year, was set up by Prime Minister David Cameron after it was revealed in July that the News of the World ordered hacking of the voicemail of missing schoolgirl Milly Dowler, who was later found murdered.
"The inquiry is beginning to receive evidence to indicate that phone hacking was not limited to that organization," said Robert Jay, counsel to the inquiry.
He said Glenn Mulcaire, who was jailed for phone-hacking in 2007 along with the News of the World's royal reporter Clive Goodman, had written the words "Daily Mirror" and "The Sun" in his notebooks, referring to other tabloids.
Jay said the names of 27 other News of the World reporters besides that of Goodman, long scapegoated by News Corp's British newspaper arm as a lone "rogue" reporter, had been found in Mulcaire's notebooks.
As police work through a list of 5,800 potential hacking victims, including actor Hugh Grant, Harry Potter author J.K. Rowling and ex-soccer star Paul Gascoigne, the scale of the scandal at and beyond the News of the World is still unclear.
News Corp executive James Murdoch, son of Chief Executive Rupert Murdoch and executive chairman of the group's British newspaper arm, is meantime fighting for his credibility as heir to the media empire.
James Murdoch has testified twice to a British parliamentary committee that he knew nothing of the scale of phone-hacking at the once best-selling tabloid, which he closed down in July in an attempt to limit the damage.
Neville Thurlbeck, a former chief correspondent at the tabloid whose name appears in a key piece of evidence, told Reuters on Monday he believed Murdoch had indeed been kept in the dark.
Murdoch's claims to have cleaned up the newspaper's culture, however, have been undermined by the News of the World's recent admission that it ordered surveillance of figures including lawyers representing hacking victims as early as this year.
Last week, Murdoch apologized to members of the parliamentary committee for the fact that the News of the World had monitored their activities.
Louise Mensch, a member of the committee, asked on Monday: "What possible public interest could there be in that? It is chilling, it's terrifying. It sort of says: 'Don't mess with us because we'll come to get you.'
"If it is true, I want to know who did the authorization, when, and on what basis, and I certainly want to see any reports that were compiled about myself and my colleagues," the Conservative member of parliament told Sky News.
Labour MP Tom Watson, the most aggressive member of the committee, pulled out of an industry event on Monday to discuss what he described as fresh evidence that News Corp spied on his colleagues.
"Under the circumstances, I have to spend the day seeking advice from the Speaker (of parliament) and discussing the matter with fellow members of the DCMS Select Committee as to our legal and constitutional position," he said.
Jay said none of the instances of phone-hacking that had so far come to light, which include eavesdropping on crime victims and relatives of war dead, came close to being justified on public-interest grounds.
"What can be justified in the public interest and how can it be justified lies at the very epicenter of this inquiry," Jay said in his opening statement.
He cited the Guardian's dogged reporting on the phone-hacking scandal, the Telegraph's exposure of members of parliament fiddling expense claims, and the Sunday Times's 1960s campaign for compensation for thalidomide victims as instances in which underhand reporting methods had been justified.
But he said the press too often went on "fishing expeditions" without any idea of what they would find, fuelling a view of the press as ruthless, unscrupulous and willing to do anything to boost circulation.
Britain's press is currently self-regulated by the Press Complaints Commission, a voluntary body with little funding and no legal powers.
Its chairperson at the time of the hacking fallout, Peta Buscombe, announced after the Milly Dowler revelations that she would step down.
The PCC is not expected to survive in its current form, and the conclusions of the Leveson Inquiry, being held at London's Royal Courts of Justice, will be important in deciding what should replace it.
"The press provides an essential check on all aspects of public life. That is why any failure in the media affects all of us," Judge Brian Leveson, who is in charge of the inquiry, said in his opening statement.
"At the heart of this inquiry therefore may be one simple question: Who guards the guardians?"
© 2014 Thomson/Reuters. All rights reserved.