British Prime Minister David Cameron condemned the alleged hacking of a murdered schoolgirl's voicemail by the News of the World, part of Rupert Murdoch's media empire, as the scandal closed in on a top News Corp executive and Murdoch protegee.

That the prime minister should find time to comment while on a visit to troops in Afghanistan was a measure of the uproar at home over suggestions that the tabloid might have hampered police and added to the torment of the family of a 13-year-old, abducted in 2002, whose killer was convicted only last month.

Among those facing new questions about their conduct is Rebekah Brooks, now head of News Corp's British newspaper arm and editor of the newspaper at the time of the murder of schoolgirl Milly Dowler -- one of Britain's highest profile crimes in years.

Brooks has until now figured only indirectly in inquiries by police into the hacking of mobile phone mailboxes by journalists and investigators employed by the News of the World.

The escalation of the scandal comes at a key moment in parent company News Corp's planned multi-billion-dollar takeover of BSkyB, due to be approved by the government after a final consultation this week.

Cameron, speaking to journalists on a visit to Afghanistan, said on Tuesday: On the question about the really appalling allegations about the telephone of Milly Dowler, if they are true, this is a truly dreadful act.

A lawyer for the Dowler family said on Monday he had learned from police that the schoolgirl's voicemail messages had been hacked while police were searching for her.

Her killer, a man with a record of other sex attacks, was found guilty of her murder last week.

British media have said a newspaper investigator not only listened in to messages left on the teenager's phone after she went missing but may also have deleted some to make space for more -- potentially misleading police and giving false hope to her family that she was still alive and at liberty.

Brooks, the editor at the time, is now chief executive of News International, News Corp's British newspaper arm. Her successor at the News of the World Andy Coulson, an ex-spokesman for Cameron, resigned from the paper over the hacking affair in 2007 and this year quit Cameron's office as the scandal grew.

Cameron, who is close to Brooks and the Murdoch family, has been at pains to keep the hacking scandal separate from a government decision to approve News Corp's planned multi-billion-dollar takeover of satellite broadcaster BSkyB.

A final public consultation on the matter ends on Friday and is expected to result in a green light from the government, although the latest development has led to renewed calls from opposition politicians to halt the merger.

BSkyB shares traded down 0.6 percent at 845 pence by 0843 GMT (4:43 a.m. ET), underperforming a flat European media index.

(Reporting by Georgina Prodhan; Editing by Alastair Macdonald)

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