The editor of one of Britain's leading tabloid newspapers resigned after a top reporter was jailed for four months for illegally tapping into over 600 mobile phone messages of the royal family's aides.
Andy Coulson, who has been editor of the News of the World, a Sunday tabloid owned by Rupert Murdoch, since 2003, said he took responsibility for the "scandal" over phone interception on Friday.
Earlier, a judge at London's Old Bailey Criminal Court sentenced Clive Goodman, the former royal editor of the News of the World, to jail, saying: "This was low conduct, reprehensible in the extreme.
"This case is not about press freedom. It is about grave, inexcusable and illegal invasion of privacy."
He added: "The targets were members of the royal family. The royal family holds a unique position in the life of this country. It is grave indeed."
Goodman, 49, had earlier pleaded guilty to the charges and was suspended from his post.
His private royal investigator, 36-year-old Glenn Mulcaire, who received six-figure sums for his research work, was sentenced to six months.
Both men had earlier admitted conspiracy to hack into the phone messages, including some from Prince William, over a period of eight months between November 2005 and June 2006.
"Research" relating to Prince Harry, his girlfriend Chelsy Davy and Sarah Ferguson, the ex-wife of Prince Andrew, was also entered on Mulcaire's expense accounts.
The lawyers for both men had earlier apologised to the princes and their father, Prince Charles, for their clients' conduct.
"The defendants' motivation was profit and personal gain and their conduct amounted to gross invasion of privacy and the abuse of the public telephone system," the court was told.
The court also heard that supermodel Elle McPherson had her home checked for surveillance devices after suspecting that her phone messages were hacked into by Mulcaire.
It is hoped that the case, the first of its kind against journalists in Britain, will in future deter the tabloid press from using illegal and intrusive methods to gain information, said commentators.