Rupert Murdoch told a British parliament hearing on Tuesday that he was shocked by the scale of hacking at the News of the World tabloid.
Murdoch's News Corporation company has come under intense criticism by politicians in Britain after it emerged that some newspaper journalists employed by the group had written stories based on material hacked from phone messages, including those belonging to crime victims, celebrities and politicians.
Murdoch, 80, accompanied by his 38-year-old son and News International chairman James, said he was "shocked, appalled and ashamed" by the fact but was not aware hacking was more widespread than originally claimed.
He said he had been misled by some of his staff.
Murdoch said he had closed the News of the World because "we were ashamed of what had happened."
The News of the World was "just 1%" of his worldwide business and he employed "people I trust to run these divisions," he said.
James Murdoch said the company failed to live up to "the standards they aspired to" and was "determined to put things right and make sure they do not happen again".
He offered "huge and sincere regret from me and my father."
James Murdoch said the company had admitted liability and set up third party schemes to pay compensation, adding they were also working closely with the police to establish where the wrongdoing was.
Asked about alleged payments to police officers by News of the World journalists and out-of-court settlements paid to victims of phone hacking, James Murdoch denied knowledge of any "improper" financial transactions.
He said it was customary to use cash in some instances, but all payments were recorded and he did not have "exact knowledge of those arrangements."
"I would like to say just how sorry I am and how sorry we are to particularly the victims of illegal voicemail interceptions and to their families," he said.
The highest-ranking casualty of the phone-hacking scandal was Paul Stephenson, who resigned as chief of the Metropolitan police service over links with Neil Wallis, former deputy editor of News of the World. Wallis was hired to advise the Metropolitan Police in 2009.
News International Chief Executive Rebekah Brooks resigned on Friday.
The News of the World, the paper at the center of most of the allegations, closed last weekend after 168 years.
The paper carried out some of its most sensational hacking activities when Brooks was editor, including breaking into the voice mail of murdered teenager Milly Dowler.
Two police inquiries are underway into the News International, one into phone hacking and one into the sale of information to journalists by police.