15 May 2012 Last updated at 06:55 ET. BBC
Q&A: News of the World phone-hacking scandal
British tabloid the News of the World closed in July 2011 after 168 years in circulation
The row over phone-hacking by journalists has led to the closure of the News of the World newspaper, the establishment of the Leveson Inquiry, an MPs' inquiry and the launch of three police investigations.
The BBC takes a look at the key questions it poses.
What is the phone-hacking scandal?
Allegations that the News of the World (NoW) had been illicitly hacking into the voicemail messages of prominent people to find stories surfaced in 2006, when NoW royal editor, Clive Goodman, and private investigator, Glenn Mulcaire, were found to have been intercepting the phones of royal aides.
The pair pleaded guilty and were jailed in 2007. The paper said they had "acted alone".
However, during the years that followed, fresh evidence of widespread hacking emerged and the number of alleged victims suing the paper grew.
A turning point came on 26 January 2011, when the Metropolitan Police opened a new investigation into phone hacking, following receipt of "significant new information" from NoW owner, News International.
The phone-hacking scandal has led to the closure of the NoW - its final edition in July 2011 included an apology and signed off with headline "Thank you and goodbye".
It has also left News Corporation with a series of problems, and has raised questions about the Met's relationship with journalists.
What was the NoW?
A national Sunday tabloid newspaper published in the UK, famed for celebrity scoops - selling an average of 2.8m copies. Its fondness for sex scandals gained it the nickname "News of the Screws".
The NoW was published by News Group Newspapers, part of News International, which is a UK subsidiary of Rupert Murdoch's News Corporation.
Claims that Milly Dowler's phone was hacked were described as "truly dreadful" by the prime minister
How many people have been hacked?
More than 4,000 people have been identified by police as possible victims of phone hacking by the NoW - with more than 1,000 likely victims.
Sportsmen, politicians and actors are among those who have already received settlements in civil cases after their phones were illegally hacked into.
Relatives of dead UK soldiers and victims of the 7/7 London bombings may also have had their phones hacked.
Further allegations have been made that journalists from other papers may also have intercepted voicemails and used "blagging" techniques.
Forty-six alleged victims of media malpractice have been given "core participant" status at the Leveson Inquiry, meaning they can be represented by a barrister and will be able to cross-examine witnesses.
Sienna Miller took legal action after her phone was hacked by NoW
How do we know who was being hacked?
The jailing of Goodman and Mulcaire stemmed from a NoW story published in November 2005 about Prince William suffering a knee injury.
Detectives recovered files from Mulcaire's home which referred to a long list of public figures and celebrities.
In 2009, the Guardian newspaper claimed NoW journalists had hacked the phones of up to 3,000 celebrities, politicians and sports stars. Police confirmed the names of some of the suspected victims. Other figures claiming to have had their phones hacked have spoken to the media.
How did the NoW hack phones?
Mobile phones used to come with a default four-digit Pin. Customers were expected to change their Pin, but very few did.
Tabloid journalists and private investigators could ring the number and if the caller didn't answer, enter the default Pin and access the person's messages.
Is phone hacking illegal?
It is against the law. If NoW bosses authorised phone hacking then they could face charges.
But the scandal also prompts wider questions about press regulation and ethics, media ownership, the police, and relationships between politicians and journalists.
What have the police done?
Sir Paul Stephenson quit as Met chief amid criticism for hiring an ex-NoW executive as an advisor
The Met has been criticised for failing to investigate phone hacking properly and of having an overly close relationship with NoW journalists.
Its initial inquiry in 2006 ended with just two arrests. In 2009, the Met chose not to relaunch their investigation, despite the Guardian's claims hacking was more widespread than one "rogue" reporter.
But in January 2011, after increased pressure from the press and civil cases brought by victims, the Met launched Operation Weeting into phone hacking.
Met officers later told MPs on the Home Affairs Select Committee that News International had tried to "thwart" the original inquiry.
Met Commissioner Sir Paul Stephenson and Assistant Commisioner John Yates resigned after criticism of police links to former News of the World deputy editor Neil Wallis. And at a judicial review in February 2012, the Met formally accepted it failed to warn people they were victims of hacking by the NoW.
Alongside its investigation into phone-hacking, Scotland Yard has since set up Operation Tuleta, examining allegations of computers being hacked to obtain private information, and Operation Elveden into alleged payments made by journalists to police and public officials.
Is anyone being prosecuted?
The first charges from the multiple investigations linked to phone hacking were announced in May 2012, when former News International chief executive Rebekah Brooks, her husband Charlie Brooks and four others were charged with conspiracy to pervert the course of justice.
Separately, Mrs Brooks - a former NoW editor - had resigned from News International because of the phone-hacking scandal in July 2011.
What have the victims done?
Dozens of celebrities and public figures are suing (or are considering suing) News International for damages over phone hacking in the civil court. A number of cases have been settled, including:
Actress Sienna Miller - £100,000 damages
Singer Charlotte Church and her parents - £600,000
Former cabinet minister Tessa Jowell - £200,000
Comedian Steve Coogan - £40,000
Sara Payne, mother of murdered schoolgirl Sarah - undisclosed damages
Other alleged victims are awaiting the outcome of police investigations or have also launched legal action.
How has the government handled hacking?
The prime minister has announced two inquiries and said the Press Complaints Commission should be scrapped.
Lord Justice Leveson is conducting a two-part inquiry, initially looking at "the culture, practices and ethics" of the UK media and its relationships with police and politicians. It will later examine the extent of unlawful conduct within newspaper groups and the police's original phone-hacking investigation.
Andy Coulson blamed coverage of the phone-hacking story for his resignation
Former Parliamentary Commissioner for Standards Elizabeth Filkin has examined the relationship between the media and police.
She concluded the "close relationship" between parts of Scotland Yard and the media had caused "serious harm". She said there were "some very serious issues" relating to contact between journalists and police which had "eroded trust from the public". Among her recommendations, she told officers to "watch out" for "late-night carousing" with journalists, and flirting.
The government, and the previous Labour administration, had also been accused of being slow to react to the scandal.
Andy Coulson - who resigned as NoW editor after Mulcaire and Goodman were jailed, but denied being aware of hacking - was later employed by David Cameron as his director of communications. He stepped down from that role in January 2011, blaming NoW coverage.
In July 2011 Mr Coulson was arrested and police searched his south London home.
This has led to questions about the judgement of David Cameron. Asked if he had "screwed up" on the decision to employ Mr Coulson, Mr Cameron said: "People will decide."
An inquiry by a cross-party committee of MPs said Rupert Murdoch was "not a fit person to exercise the stewardship of a major international company". Its report published in May 2012 concluded Mr Murdoch exhibited "wilful blindness" to what was going on in his media empire. The committee was split on party lines over a number of key findings - including the verdict on Rupert Murdoch - with the Tories voting against and Labour and the Lib Dems in favour.
The committee also said the News of the World and News International misled Parliament about the scale of phone hacking. The cross-party culture committee questioned journalists and bosses at the now closed paper, as well as police and lawyers for hacking victims.
How is hacking linked to alleged payments to police?
Commentators and victims accused the police of a lack of will to investigate hacking because officers were too close to the media.
At the beginning of July 2011, News International handed over emails which were said to show payments were made to police in return for information, and they were alleged to have been authorised by Mr Coulson.
The then Met Commissioner Sir Paul Stephenson had said a small number of officers were alleged to have taken illegal payments, and if true, they would face a criminal court.
A number of police and former officers have so far been arrested.
Former NoW editor Rebekah Brooks has stepped down as chief executive of News International
How has News International responded to the scandal?
News Corp boss Rupert Murdoch issued an apology for the "serious wrongdoing" by the NoW, in UK national newspaper adverts.
In April 2011, News International admitted hacking was used and issued an apology. It has made several payouts.
On 19 July 2011, Rupert Murdoch and James Murdoch gave evidence to the House of Commons Culture, Media and Sport Select Committee and denied knowing the full extent of the allegations until evidence in civil cases was requested in late 2010.
James Murdoch told MPs he had not been "aware" of an email suggesting hacking went beyond a single "rogue" reporter. Two former News of the World executives later issued a statement claiming they had informed him of the email but Mr Murdoch responded by saying he stands by his testimony.
A letter from the former royal editor Clive Goodman, which alleges senior NoW figures knew what was going on, was released by MPs on 15 July 2011.
James Murdoch was questioned again by the media committee in November 2011 and reiterated his claim that he had been unaware of the scale of phone hacking.
Both James and Rupert Murdoch appeared before the Leveson Inquiry in April 2012.
Heather Mills claims a Mirror Group journalist admitted hacking her phone
Were other papers involved in phone hacking?
Questions have been raised about the conduct of journalists at the Trinity Mirror group of newspapers. The group, which publishes titles including the Daily and Sunday Mirror, Daily Record and People, says all its journalists work within the law.
However, a journalist who worked at the Sunday Mirror in the last decade has told the BBC they witnessed routine phone hacking in the paper's newsroom.
Model Heather Mills has alleged that a senior Mirror Group journalist admitted hacking her voicemails after quoting passages verbatim.
Parent group Trinity Mirror says all its journalists work within the law.
And former Daily Mirror editor Piers Morgan has denied that comments he made in previous interviews amounted to an admission he knew about phone hacking at the paper, and says he never hacked a phone or told anyone to do so.
Actor Hugh Grant has accused the Daily Mail of hacking phones, but the paper's editor has denied this.
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