Rupert Murdoch\'s News Corp., whose share price has fallen nearly 15 percent amid a spiraling telephone-hacking scandal in Britain, announced a $5 billion stock repurchase plan on Tuesday. News Corp. said its board of directors had approved a plan to increase the $1.8 billion remaining in its current stock buyback program to $5 billion. \"News Corporation is targeting to acquire the $5 billion of Class A common stock and Class B common stock from time to time over the next 12 months,\" News Corp. said in a statement. It said the purchases would begin after August 15. News Corp. shares have lost 14.6 percent on Wall Street over the past week as the scandal that led to the closure of the News of the World tabloid shows no signs of abating and is threatening the company\'s multi-billion dollar bid to win full control over British satellite broadcaster BSkyB. News Corp. shares were up 0.06 percent at $15.49 in early afternoon trading on Wall Street. In a fresh blow to the global media and entertainment giant, a group of US investors who sued News Corp. earlier this year have amended their lawsuit to reflect the fallout from the phone-hacking scandal. Two pension funds and New York-based Amalgamated Bank, which manages about $12 billion for institutional investors, accused Murdoch of \"a long history of abuses\" in their lawsuit, filed in March. New allegations that the News of the World hacked the voicemail of a murdered girl and slain British soldiers led the plaintiffs to add fresh ammunition to their legal challenge this week. \"These revelations show a culture run amuck within News Corp and a Board that provides no effective review or oversight,\" reads the amended lawsuit, which was filed in the US state of Delaware. \"It is inconceivable that Murdoch and his fellow Board members would not have been aware of the illicit news gathering practices,\" it said. The lawsuit was originally filed to challenge News Corp.\'s $675-million acquisition of Shine, a television and film production company run by Rupert Murdoch\'s daughter Elisabeth. The lawsuit denounced the deal as part of a pattern of \"rampant nepotism,\" stating: \"Throughout his tenure, Murdoch has treated News Corp like a family candy jar, which he raids whenever his appetite strikes.\" Australian-born Murdoch has built News Corp. into a huge media empire which spans newspapers, television and Hollywood movies and wields immense political influence. Rupert Murdoch flew into London on Sunday to take charge of a crisis which sparked the closure of the 168-year-old News of the World tabloid, which had been a major part of News Corp.\'s British division News International. British lawmakers took advantage of his presence to call on him, his son, News Corp. executive James Murdoch, and News International chief executive Rebekah Brooks to appear to face questions about hacking and allegations that Murdoch papers paid police for information.