LONDON (AFP) - Rupert Murdoch said Tuesday he faced "the most humble day of my life" but denied ultimate responsibility for the phone-hacking scandal as the media mogul and his son faced a grilling from British lawmakers. In testimony that at times stumbled to a halt, the 80-year-old News Corporation chief said he was appalled by the activities of the shuttered News of the World newspaper but shifted the blame onto the people who worked for him. He also told a parliamentary committee there was no evidence the tabloid hacked the phones of 9/11 victims, a key allegation being investigated by the FBI that could threaten his US operations. "This is the most humble day of my life," the Australian-born Rupert Murdoch said in a brief opening statement to the British parliament's Culture, Media and Sport committee. The scandal over the hacking of voicemails at the News of the World has rocked Murdoch's empire, sparked the resignation of two of Britain's top police establishment, and even placed Prime Minister David Cameron under pressure. Former News International chief executive Rebekah Brooks was due to testify later. Murdoch, whose Chinese-born wife Wendi was also in the room, said it was "not an excuse" but that with an empire of 53,000 staff to oversee he could not be held fully responsible for failing to uncover the scandal. He said that the company took swift action when it became aware of fresh phone-hacking evidence following a series of civil actions in 2010, but he denied knowing that the company had made payments to some high-profile victims. Asked by opposition Labour lawmaker Jim Sheridan "Do you accept that ultimately you are responsible for this whole fiasco?", Murdoch tersely replied: "No". When pressed over who he blamed, Murdoch said: "The people that I trusted to run it (his media empire) and then maybe the people they trusted." He said he was "absolutely shocked, appalled and ashamed when I heard about the Milly Dowler case two weeks ago," referring to the case of a murdered teenager whose phone was allegedly hacked by the News of the World. Murdoch was also asked about claims the paper targeted the voicemails of victims of the September 11, 2001 attacks in the United States, but replied: "We have seen no evidence of that at all and as far as we know the FBI haven't either." At times James, 38, the chairman of Murdoch's British newspaper operation News International, tried to step in when his father faltered on a question but was several times slapped down by lawmakers. "I would like to say just how sorry I am and how sorry we are to particularly the victims of illegal voice mail interceptions and to their families," James Murdoch said. The Murdochs initially refused to appear before the committee but relented after they were formally summoned. They appeared shortly after Cameron, who has faced pressure over his own close friendships with a number of current and former Murdoch aides, cut short a trip to Africa so he could return to address parliament on Wednesday. "This is a big problem but we are a big country," Cameron said after meeting Nigerian President Goodluck Jonathan in Lagos.