Britain's phone hacking scandal came knocking on the door of Downing Street Thursday, as Prime Minister David Cameron's former communications chief faced a grilling by a media ethics inquiry about his time as editor of a tabloid newspaper that practiced large-scale illegal eavesdropping.

Andy Coulson has always insisted he did not know that News of the World employees were hacking the voice mail messages of celebrities, politicians and even crime victims in its quest for scoops and circulation.

He left the paper in 2007 after a reporter and a private investigator were jailed for hacking, and became Cameron's powerful media chief later the same year. He quit that job in January 2011 as the hacking scandal intensified.

Coulson was due to appear at the inquiry after Jonathan Harmsworth, also known as Viscount Rothermere, the aristocratic owner of the Daily Mail and Mail on Sunday newspapers.

Those papers and their hugely popular website have flourished on celebrity exposes, but no evidence has emerged of phone hacking, and Harmsworth said his conscience is clear.

"I feel pretty confident that our newspaper has acted ethically and I am willing to stand up for us," he said.

Coulson's appearance at the inquiry — which is examining the often too-cozy relationship between British politicians and the country's press — will be uncomfortable for the Conservative prime minister, whose relationships with senior executives of Rupert Murdoch's News Corp. has embroiled him in the hacking furor.

Cameron has close ties to Coulson and to Rebekah Brooks, another ex-news of the World editor, who is due to give evidence to the inquiry on Friday.

Both Coulson and Brooks have been arrested and questioned by police about tabloid wrongdoing, though neither has been charged.

Speculation is rife about what the pair will reveal about their relations with Cameron and his Conservative Party, whose popularity is already at a low amid economic uncertainty and unrest from grassroots activists.

The Murdoch-owned Times of London newspaper reported Wednesday that Brooks has retained supportive text messages from the prime minister, a personal friend, neighbor and occasional riding companion in the upmarket rural enclave of Chipping Norton.

Brooks and Coulson will be testifying before Lord Justice Brian Leveson, who is leading the inquiry to sift through the fallout of the hacking scandal that has rocked Britain's establishment and rattled Murdoch's News Corp. with revelations of widespread journalistic malpractice.

The inquiry has heard from reporters, police and public figures in an effort to understand why nothing was done to stop the phone hacking for so long.

Murdoch shut the 168-year-old News of the World in July after evidence emerged that it had intercepted the phone messages of a missing schoolgirl, Milly Dowler, who was later found murdered.

Murdoch has so far paid out millions to settle lawsuits from 60 actors, athletes, politicians and other public figures whose voice mails were hacked. Dozens more lawsuits have been filed.


Associated Press Writer Raphael Satter contributed to this report.