Rupert Murdoch today condemned allegations that staff at the News of the World hacked phones and paid police officers as "deplorable and unacceptable".
But the media mogul backed Rebekah Brooks to continue as chief executive of News International, the paper's publisher.
His statement, following allegations that murdered schoolgirl Milly Dowler's mobile phone was hacked, came as David Cameron bowed to mounting pressure to hold a public inquiry into the scandal and MPs lined up to condemn journalistic practices at the News of the World in an emergency debate in the House of Commons.
Mr Murdoch, who is chairman and chief executive of News International's parent company, News Corporation, said: "Recent allegations of phone hacking and making payments to police with respect to the News of the World are deplorable and unacceptable.
"I have made clear that our company must fully and proactively cooperate with the police in all investigations and that is exactly what News International has been doing and will continue to do under Rebekah Brooks' leadership.
"We are committed to addressing these issues fully and have taken a number of important steps to prevent them from happening again.
"I have also appointed Joel Klein to provide important oversight and guidance and Joel and Viet Dinh, an independent director, are keeping News Corporation's board fully advised as well."
The Prime Minister will hold talks with party leaders about plans for inquiries into phone hacking.
Downing Street aides insisted they wanted it to be "independent" and "public" but refused to say what format it would take.
The Prime Minister's spokesman said: "We want to make sure it has public confidence.
"He certainly thinks this needs to be an independent process and a public process.
"We will think about precisely how it is run.
"I don't think it would be sensible to set out timeframes at the moment."
Calls have been made for the Government to reassess plans to allow the full takeover of BSkyB by News Corp.
Downing Street insisted it was a quasi-judicial process and Culture Secretary Jeremy Hunt would consider representations made to the consultation on the proposals, which ends at midday on Friday.
Ofcom is obliged to assess whether licence holders are fit and proper on an "ongoing basis", without any need for ministerial direction, the spokesman added.
No conversations have been held with Rebekah Brooks, Andy Coulson or James Murdoch since the revelations.
The Prime Minister only found out about the latest batch of revelations when they appeared in the media, his aides insisted.
Asked about Mr Coulson's assurances before he took up the position of communications director, the spokesman said: "The Prime Minister's position on this is that he was given assurances at the time, which he accepted.
"He felt during his period in government Andy Coulson did a very good job.
"There is now a police investigation under way and we should let the police get on with it."
Downing Street is due to host The Sun's police bravery awards tomorrow but aides refused to say if any News International executives would attend.
Mr Murdoch's intervention came amid mounting political and commercial pressure over claims that the News of the World hacked the phones of murder victims and their families.
Labour leader Ed Miliband joined other MPs in calling for the sacking of Ms Brooks, who was the Sunday tabloid's editor when a private investigator allegedly intercepted murdered schoolgirl Milly Dowler's voicemail.
Labour MP Tom Watson even demanded the suspension of James Murdoch, Mr Murdoch's son and the chairman of News International.
Meanwhile, more companies announced they were cancelling advertising due to appear in this weekend's edition of the News of the World.
Halifax and the Co-operative Group, which each had two half-page adverts last Sunday, joined Ford, Vauxhall, Mitsubishi, Butlins and Virgin Holidays in suspending their marketing in the paper.
Mr Cameron told MPs at Prime Minister's question time that he supported holding one or more inquiries into the phone hacking scandal.
He said: "We are no longer talking here about politicians and celebrities, we are talking about murder victims, potentially terrorist victims, having their phones hacked into.
"It is absolutely disgusting, what has taken place, and I think everyone in this House and indeed this country will be revolted by what they have heard and what they have seen on their television screens."
Mr Cameron said there were two "vital areas" that needed to be considered - why the original police inquiry failed to "get to the bottom of what happened", as well as the behaviour, practices and ethics of journalists and media organisations.
"Clearly, we can't start all that sort of inquiry immediately because you must not jeopardise the police investigation, but it may be possible to start some of that work earlier," he said.
He offered to hold talks on the matter with other party leaders, Attorney General Dominic Grieve and Cabinet Secretary Sir Gus O'Donnell.
Speaking for the Government during a three-hour emergency Commons debate on the latest revelations, Mr Grieve indicated that inquiries could be set up and begin some aspects of their work before criminal investigations were complete.
Mr Cameron said he took "full responsibility" for his decision to employ former News of the World editor Andy Coulson as his most senior spin doctor - a position he quit in January.
The ex-Downing Street director of communications was drawn further into the row with claims that he had authorised payments to police when he edited the newspaper, a matter he denied on behalf of News International giving evidence in 2003.
Metropolitan Police Commissioner Sir Paul Stephenson said News International had given Scotland Yard documents which include information relating to "inappropriate payments to officers" in his force.
News International said in a statement: "The fact that these developments came as a result of voluntary disclosure demonstrates not only full co-operation with the Metropolitan Police Service but also News International's determination as a company to deal responsibly and correctly with the issues that have arisen."
Families of 7/7 bombing victims have also been told their phones might have been targeted for hacking.
And police have confirmed that the parents of murdered Soham schoolgirls Holly Wells and Jessica Chapman were contacted by detectives from the News of the World hacking inquiry team.
News International executives said today they were "very close" to discovering who commissioned private investigator Glenn Mulcaire to allegedly hack Milly's phone after she went missing in 2002.
Simon Greenberg, the company's director of corporate affairs, said he was "clear" that the individual was not Ms Brooks.
News International has established that Ms Brooks was on holiday in Italy when the News of the World ran a story referring to a message left on Milly's phone, the Guardian reported.
The company also believes she was away in the fortnight after the Soham murders, the paper said.
Labour MP Chris Bryant, who secured the parliamentary debate, suggested there could be other high-profile victims of phone hacking.
He told the Commons: "I am told that police are looking at not just Milly Dowler's phone and those of the families of Holly Wells and Jessica Chapman, but the case of Madeleine McCann and 15-year-old Danielle Jones who was abducted and murdered in Essex in 2001 by her uncle Stuart Campbell."
Ms Brooks has pledged her "full co-operation" with the police inquiry, said she was "sickened" by the allegations and promised the "strongest possible action" against those responsible.