LONDON — Media titan Rupert Murdoch and his son James refused Thursday to appear in public next week before a parliamentary committee investigating phone hacking and bribery by employees of their British media empire, whose chief executive said that she would address the committee.

The chairman of the Culture, Media and Sport committee said it had issued summonses to the Murdochs but it was unclear if Rupert Murdoch could be compelled to testify because he is a US citizen.

In a letter to the committee, James Murdoch, the chief of his father's European and Asian operations, offered to appear in August.

Rupert Murdoch said he would appear before a separate inquiry initiated by Prime Minister David Cameron and led by a judge, and was willing to discuss alternative ways of providing evidence to parliament.

News International chief Rebekah Brooks, a British citizen, said that she would appear Tuesday, chairman John Whittingdale said.

Meanwhile, the criminal investigation into the Murdoch empire widenened as the former deputy editor of the News of the World was arrested by detectives probing phone hacking at the defunct tabloid.

Metropolitan Police said Neil Wallis, deputy editor under Andy Coulson from 2003 to 2007, was arrested on suspicion of conspiring to intercept communications. They did not confirm that it was Wallis.

Police have so far arrested seven people for questioning in their investigation of phone hacking and two others in a separate investigation of alleged bribery of police officers. No one has been charged.

Coulson, Cameron's communications director from 2007 until January this year, was arrested on July 8.

Deputy Prime Minister Nick Clegg said Murdoch had big questions to answer about the accusations of eavesdropping and police bribery at his British papers, which have forced the media titan to drop his bid to take full control of British Sky Broadcasting.

"If they have any shred of sense of responsibility or accountability for their position of power, then they should come and explain themselves before a select committee," Clegg said in an interview with BBC radio.

Brooks was editor of News of the World in 2002 at the time of the most damaging allegation so far, that the paper hacked into the phone of teenage murder victim Milly Dowler in 2002 and may have impeded a police investigation into the 13-year-old's disappearance.

Brooks has said she was unaware of any phone hacking at the time.

Murdoch's hope of making BSkyB a wholly owned part of his News Corp. empire collapsed on Wednesday in the face of what Cameron called a "firestorm" that has engulfed media, police and politicians.

Cameron has appointed a judge for a wide-ranging inquiry into the News of the World scandal and wider issues of media regulation, the relationship between politicians and media and the possibility that illegal practices are more widely employed in the industry.

"It clearly goes beyond News International," Clegg said.

"It is clearly something much more systemic," Clegg said. "I don't think we should allow ourselves to believe that it is just because of the Murdochs, or Rebekah Brooks, or it's all about one commercial transaction, however significant."

Shares in BSkyB opened higher in London on Thursday but retreated toward noon to trade down 0.6 percent at 701.5 pence ($11.30). The shares closed higher on Wednesday for the first time since they began falling sharply last week amid fresh phone hacking allegations.