British Prime Minister David Cameron's former media chief Andy Coulson was jailed for 18 months on Friday for his complicity in widespread phone-hacking by journalists to obtain scoops at the Rupert Murdoch-owned tabloid he edited.

Coulson, editor of the now defunct News of the World newspaper from 2003-2007, was convicted last week of conspiracy to intercept voice mails on mobile phones following a high-profile eight-month trial at London's Old Bailey court.

The prime minister, who has apologized for having hired Coulson, said of the sentence: "What this says is that it's right that justice should be done and that no one is above the law".

Opposition leader Ed Miliband has criticized Cameron for bringing a "criminal into the heart of Downing Street".

The maximum sentence the 46-year-old could have faced was two years but the judge said he had taken into account Coulson's good character. He showed no reaction as the sentence was read out in a packed Court 12 at the Old Bailey.

"Mr Coulson on the jury's verdict has to take the major blame for the phone hacking at the News of the World," judge John Saunders said. "He knew about it and encouraged it when he should have stopped it."

The sentence was handed down exactly three years to the day that the Guardian newspaper published revelations that staff on the paper had hacked into the voice mails of murdered schoolgirl Milly Dowler.

That sparked widespread outrage across the country, which forced Murdoch to close the 168-year-old tabloid just days later. It emerged that the newspaper had listened into messages of countless targets - from movie stars to crime victims to government ministers - to obtain information for scoops.

Coulson was the only one of seven defendants to be convicted following the long-running trial.

He was found guilty of conspiracy to illegally intercept voice mails on mobile phones. The jury failed to reach a verdict on charges he authorized illegal payments to public officials, and he is to be retried at a later unknown date.

Three other senior journalists from the paper - Greg Miskiw, Neville Thurlbeck and James Weatherup - had pleaded guilty before the trial began and were also sentenced on Friday. Miskiw and Thurlbeck were sentenced to six months in jail while Weatherup was given a 4-month suspended sentence.

Glenn Mulcaire, the former private investigator who conducted much of the hacking and who has already gone to jail for an earlier hacking offense, was given a six-month suspended sentence.

Coulson's one-time lover Rebekah Brooks, his predecessor as News of the World editor who later ran News Corp's British newspaper arm, was found not guilty of phone-hacking and other allegations last week by the jury.

Phone-hacking became public knowledge in 2006 when the News of the World's former royal editor Clive Goodman and Mulcaire admitted they had hacked the phones of royal aides. The paper said at the time that Goodman was a rogue reporter acting alone to hire Mulcaire.