Detectives reopened the case earlier this year and are looking at a potential 3,700 victims.
The scandal has prompted the resignation and subsequent arrest of Brooks and the resignation of Wall Street Journal publisher Les Hinton, sunk the Murdochs' dream of taking full control of lucrative satellite broadcaster British Sky Broadcasting and raised questions about his ability to keep control of his global media empire.
Rupert Murdoch is eager to stop the crisis from spreading to the United States, where many of his most lucrative assets — including the Fox TV network, 20th Century Fox film studio, The Wall Street Journal and the New York Post — are based.
London's departing police chief revealed that 10 of the 45 press officers in his department used to work for News International, but he denied there are any improper links between the force and Murdoch's media empire.
"I understand that there are 10 members of the (Department of Public Affairs) staff who have worked in News International in the past, in some cases journalists, in some cases undertaking work experience with the organization," Paul Stephenson said.
News International is the British newspaper division of Murdoch's global News Corp.
Stephenson denied wrongdoing, or knowing the News of the World was engaged in phone hacking — but acknowledged that in retrospect he was embarrassed the force had hired Neil Wallis, a former executive of the paper, as a PR consultant,
After being asked about his relationship with Wallis, who was arrested last week, Stephenson said he had "no reason to connect Wallis with phone hacking" when he was hired for the part-time job in 2009.
He said now that the scale of phone hacking at the paper has emerged, it's "embarrassing" that Wallis worked for the police.
Stephenson announced his resignation Sunday, saying allegations about his contacts with Murdoch's News International were a distraction from his job.
He was followed out the door by assistant commissioner John Yates, who gave evidence before the hotly anticipated appearance by the Murdochs and Brooks.
Yates said that with the benefit of hindsight he would have re-opened an inquiry into electronic eavesdropping of voicemail messages.
Yates said if he "knew now" how the phone hacking scandal would enfold, he would have done something different.
He has denied wrongdoing in the scandal.
London's Metropolitan Police force said Tuesday it had asked a watchdog to investigate its head of public affairs over the scandal — the fifth senior police official being investigated. The Independent Police Complaints Commission will look at Dick Fedorcio's role in hiring a former News of the World executive as an adviser to the police.
Fedorcio also was questioned by lawmakers Tuesday, along with Stephenson and Yates.
But it was the appearance by the Murdochs and Brooks that was drawing huge public interest.
Murdoch's car was mobbed by photographers as he arrived for the hearing about the scandal, which has swept from his media empire through the London police and even to the prime minister's office.
The Range Rover quickly drove off, returning returned to Parliament about half an hour before the hearing was due to start.