Former Number 10 communications adviser Andy Coulson has been jailed for 18 months after being found guilty of plotting to hack phones while in charge at the News of the World.
Judge Mr Justice Saunders said Coulson clearly thought it was necessary to use phone hacking to maintain the newspaper's "competitive edge".
He said: "Mr Coulson has to take the major share of the blame of phone hacking at the NotW. He knew about it, he encouraged it when he should have stopped it."
ITV News Political Correspondent Romilly Weeks reports:
The delay in the News of the World telling police about the Milly Dowler voicemail in 2002 showed the motivation was to "take credit for finding her" and sell the maximum number of newspapers, he added.
Prime Minister David Cameron said the jailing of the former Downing Street director of communications showed that "no one is above the law."
The paper's former news editor Greg Miskiw, was also jailed for six months jail for being complicit in industrial scale phone-hacking and journalist James Weatherup was handed a four month sentence, suspended for 12 months, for conspiring to hack phones.
However, private detective Glenn Mulcaire will not go to jail despite admitting to his role in the phone hacking.
The judge described Mulcaire, 43, as "the lucky one," saying it would be wrong to jail him again after he already served a sentence in 2006 when he was first convicted of phone hacking.