Stephenson's announcement came hours after Rebekah Brooks, former chief of Murdoch's British operations, was arrested on suspicion of conspiring to intercept private voice-mail messages and corruption charges stemming from bribes allegedly paid to police officers by journalists in exchange for information.
The two surprising developments are certain to focus greater attention on Murdoch's scheduled appearance Tuesday before a parliamentary committee to answer questions on the allegations of large-scale cellphone hacking by the News of the World, a now-defunct tabloid owned by his media conglomerate News Corp.
The scandal has reached far beyond the media to envelop the police, who have been accused of conducting a halfhearted investigation into the hacking allegations in order to preserve a good relationship with the press, and high-ranking politicians, who have also been criticized for maintaining too-cozy ties with the media, Murdoch's newspapers in particular.
Public confidence in key institutions of British society - the police, politicians and the press - has now been badly shaken.
Stephenson acknowledged that Scotland Yard's initial inquiry of allegations of phone hacking by the News of the World several years ago was inadequate, though he said he could only rely on the word of his subordinates that the investigation had been thorough and successful.
Stephenson said he was unaware of the existence of about 11,000 pages of evidence seized from a private investigator hired by the News of the World - papers that showed the tabloid may have ordered the hacking of the cellphones of nearly 4,000 people, including celebrities, politicians and crime victims.
Still, "as commissioner, I carry ultimate responsibility for the position we find ourselves in. With hindsight, I wish we had judged some matters involved in this affair differently. I didn't and that's it," he said in a videotaped statement.
