LONDON, UK: Prime Minister David Cameron will be grilled by parliament on Wednesday about his decision to employ a former tabloid newspaper editor caught up in a phone-hacking scandal that has rocked Britain's establishment.

The scandal, centred on Rupert Murdoch's News Corp global media empire, has forced the resignations of senior executives at the company and two of Britain's top policemen as well as fuelling opposition attacks on Cameron's judgment.

The 80-year-old Murdoch was attacked by a protester with a foam pie when he appeared before a parliamentary committee on Tuesday and made a "humble" apology for the scandal but refused to resign. He said staff who "betrayed" him were at fault.

Analysts said Murdoch's televised apology had now put the spotlight on how Cameron emerges from scrutiny in the emergency parliamentary debate over the scandal, which has included allegations of hacking into a murdered schoolgirl's voicemail and the phones of British troops killed in combat.

The scandal is unlikely to bring down Cameron, in office for less than 15 months, but could make it harder for him to manage a Conservative-led coalition that is focused on quick deficit reduction, which has labour unions threatening mass strikes.

Cameron cut short a trip to Africa for the debate, with the opposition Labour Party determined to put him on the rack over why he employed Andy Coulson, a former editor of Murdoch's News of the World tabloid, since shut down over the scandal.

"The Murdochs can say they apologised unreservedly, they faced the music, (and) they endured a personal physical attack," said Andrew Hawkins of polling company Comres.

"It puts the attention firmly back on the political ramifications and, in particular, David Cameron and his judgment over the whole Andy Coulson issue," said Hawkins.

Labour leader Ed Miliband has already put pressure on Cameron over Coulson, who resigned as editor of the News of the World but denied any wrongdoing after two people employed by the newspaper were convicted of phone-hacking in 2007.

Then opposition leader Cameron appointed Coulson as his communications chief that year and kept him on becoming prime minister in May 2010. He has said he gave Coulson the job because there was no evidence of his involvement in hacking.

Coulson quit his government role in January when police launched a new investigation, and Miliband turned up the heat on Cameron when the former editor was arrested for questioning earlier this month and then freed on bail.

Speaking in Nigeria before flying home, Cameron signalled a desire to push the agenda away from a scandal that has dominated every debate for two weeks.

"The British public want something else too," Cameron said.

"They don't want us to lose our focus on an economy that provides good jobs, on an immigration system that works for Britain, a welfare system that is fair for our people."

"HUMBLE" MURDOCH

Calling it "the most humble day of my life", Murdoch defended his record and that of his son and top News Corp executive James, and said he could not know everything all his 53,000 employees did.

James, 38, sat beside him before parliament's media committee, interjecting on occasion as his father hesitated to give answers on what he knew about hacking and payments made to some of those involved.