The British prime minister's powerful spin doctor resigned Friday amid claims he sanctioned widespread illegal hacking of cell phones belonging to politicians, celebrities and royalty when he was editor of a top-selling tabloid newspaper.
Andy Coulson denies any knowledge of the hacking, but admitted he had committed a cardinal sin for a back room operator -- he became the story.
Coulson said "continued coverage of events connected to my old job at the News of the World has made it difficult for me to give the 110 percent needed" in his role as Downing Street communications chief.
"I stand by what I've said about those events but when the spokesman needs a spokesman, it's time to move on."
A reporter and a private investigator working for the News of the World were caught illegally eavesdropping on the phones of the British royal family's entourage in 2007. Coulson quit the newspaper when the pair were convicted, but says he knew nothing of the hacking.
His resignation is a blow to Prime Minister David Cameron, who has resisted calls to fire Coulson despite the scandal.
It will bolster those skeptical of claims by the Rupert Murdoch-owned newspaper that a couple of rogue employees had hacked the cell phones.
Cameron said that he was very sorry Coulson had quit, and believed his claim that he was ignorant of the spying.
"Andy Coulson resigned from the News of the World when he found out what was happening," Cameron said. "I've always felt he's been punished for the same offense twice."
The weekly News of the World, with a circulation of more than 3 million, thrives on celebrity exclusives. The subjects of those stories have long puzzled over how the newspaper got its inside information. Many thought they had their answer when news of the phone hacking broke.
A police inquiry turned up thousands of numbers of potential phone-tapping targets, including celebrities, sports stars and senior politicians. The hacking worked by exploiting lax cell phone security to tap into targets' phones and eavesdrop on their voice mail messages.
Last year, the New York Times and the Guardian newspapers quoted former News of the World reporters as saying Coulson knew about the phone hacking, which they claimed was widespread at the newspaper.