Bloomberg reports:

News Corp. (NWSA)’s Rupert Murdoch is struggling to control the destiny of the company he began building six decades ago after a trusted deputy was arrested and Scotland Yard’s top official quit over ties to a suspect in the phone-hacking probe.

Independent directors of New York-based News Corp. have begun questioning the company’s response to the crisis and whether a leadership change is needed, said two people with direct knowledge of the situation who wouldn’t speak publicly. Rebekah Brooks, the former News International chief who Murdoch backed until last week, was arrested yesterday in London.

“The shell of invulnerability that Rupert Murdoch had around him has been cracked,” said James Post, a professor at Boston University’s School of Management who has written about governance and business ethics. “His credibility and the company’s credibility are hemorrhaging.”

Murdoch and his 38-year-old son, James Murdoch, are spending most of their time with advisers preparing for tomorrow’s hearing before a U.K. parliamentary committee. They will face questions over their role in and responsibility for phone hacking that took place at their now-defunct News of the World tabloid. The company took out advertisements in national U.K. newspapers this weekend to apologize for the scandal.

News Corp. (NWS) fell 66 cents, or 4.2 percent, to $14.98 on the Nasdaq Stock Market at 11:18 a.m. New York time. Before today, it had lost 13 percent since July 4, when the Guardian reported that News of the World employees had intercepted the voice mail of Milly Dowler, a schoolgirl who was later found murdered. The tabloid is also alleged to have hacked into the phones of terror victims and dead soldiers, as well as politicians and celebrities.

The slump has shaved more than $6 billion off the combined value of the Class A shares and the Class B voting stock that gives the Murdochs control over the company.