Coulson, who was forced to resign from his Downing Street post over the scandal, now faces the possibility of up to two years in jail following an eight- month trial at the Old Bailey.
The jury of eight women and three men who convicted Coulson cleared ex-News International (NI) chief executive Rebekah Brooks of all charges, including conspiring to hack phones and conspiring to pervert the course of justice.
Mrs Brooks’ husband, Charlie Brooks, and her former personal assistant, Cheryl Carter, were also acquitted.
The jury has yet to return verdicts on two further charges facing Coulson and former News of the World (NotW) royal editor Clive Goodman, of conspiring to commit misconduct in a public office by paying police officers for two royal directories.
Coulson, 46, of Charing, Kent and Goodman, 56, of Addlestone, Surrey, deny the charges. After the guilty verdict, Prime Minister David Cameron issued a “full and frank” apology for giving Coulson a job.
“I take full responsibility for employing Andy Coulson. I did so on the basis of undertakings I was given by him about phone hacking and those turned out not to be the case,” he said.
“I always said that if they turned out to be wrong, I would make a full and frank apology and I do that today. I am extremely sorry that I employed him. It was the wrong decision and I am very clear about that.”
Chancellor George Osborne added: “We gave him a second chance but, knowing what we now know, it’s clear that we made the wrong decision.”
But Labour leader Ed Miliband said that the apology did not go far enough, and the Prime Minister had “very serious questions to answer” about why he stuck by Coulson long after serious allegations about him had become public.
Mr Cameron had “brought a criminal into the heart of Downing Street” and his government was “tainted” as a result, said Mr Miliband, who accused the Prime Minister of putting his relationship with News Corporation chairman Rupert Murdoch ahead of the public interest.
Coulson, a married father of three, was recruited by Mr Osborne to head up the Conservative media operation within months of resigning as NotW editor in 2007. When Mr Cameron entered Downing Street in 2010, Coulson became No10’s chief spin doctor, quitting shortly before he was arrested over the phone-hacking scandal.
Last night, judge Mr Justice Saunders urged restraint to anyone planning to comment on the case until all verdicts have been returned.
Standing in the dock alongside Mrs Brooks, Charlie Brooks and Cheryl Carter, Coulson showed no emotion when the verdict was read out.
Mrs Brooks, who preceded Coulson as editor of the now defunct NotW, left court with her husband and got into a taxi without speaking to reporters.
The partial verdicts were delivered on the jury’s eighth day of deliberations and the 138th day of the trial.
Mrs Brooks, 46, was cleared of hacking, misconduct in a public office for allegedly signing off payments to a Sun journalist’s “number one military contact” between 2004 and 2012, conspiracy to pervert the course of justice and perverting the course of justice.
Retired managing editor Stuart Kuttner, 74, was also cleared of being part of the hacking conspiracy spanning six years.
Mrs Brooks’ former personal assistant Cheryl Carter, 50, of Chelmsford, Essex, was cleared of perverting the course of justice by removing seven boxes from the NI archive just days before she was arrested in 2011.
Racehorse trainer Mr Brooks, 52, of Churchill, Oxfordshire, and NI head of security Mark Hanna, 51, were cleared of perverting the course of justice.
After Goodman and private detective Glenn Mulcaire were convicted of hacking in 2006, they were alleged to have been involved in a cover-up to keep the full extent of phone hacking secret.
Mrs Brooks was the editor when Mulcaire received his first annual contract with the paper for £92,000 in 2001. She was still in charge in 2002 when he hacked the phone of murdered schoolgirl Milly Dowler – an act which led to the eventual downfall of the Sunday tabloid.
But it was after Coulson took over the editorship in 2003 and mrs Brooks moved to the Sun that hacking really took off at the NotW, the court heard.
Goodman, 56, said it was going on on an “industrial scale”, while reporter Dan Evans told jurors even the “office cat” knew.
A host of politicians, sports people, celebrities, and members of the royal family were targeted by NotW staff and Mulcaire.
An e-mail about Calum Best in which Coulson wrote “do his phone” was, the prosecution said, a direct hacking order.
Last night Bob Satchwell, executive director of the Society of Editors, said: “After a hugely expensive investigation and criminal trial, the jury concluded that what was suggested to be a major conspiracy at the top of NI was not all that it seemed.”
Hacking victim and actress
Sienna Miller, who gave evidence during the trial, told ITV News: “It happened, it’s really unfortunate and it does make me incredibly angry but I do feel like justice is being done.”
Brian Cathcart, of the Hacked Off group, said: “For years the Murdoch press clung to the story that one rogue reporter was responsible for phone hacking. We now know this was a lie. Far from being an isolated incident involving a few ‘bad apples’, the trial has shown that the entire orchard was rotten.”
A spokesperson for News UK – the British publishing arm of Mr Murdoch’s media empire – said they had put in place measures to ensure that the wrongdoing at the NotW could not happen again.
The trial continues today.