LONDON (Reuters) - A former newspaper executive whose emails led to the exposure of widespread phone-hacking at Rupert Murdoch's now-defunct British tabloid, the News of the World, was jailed for eight months on Friday.

Ian Edmondson, 45, worked as news editor on the paper, which was closed three years ago when revelations about the extent of criminal activity became public, sending shockwaves through Murdoch's News Corp and the British establishment.

Edmondson admitted last month conspiring with colleagues to illegally access voicemails, and has been linked to 334 hacking cases, with the victims including actors Jude Law and Sienna Miller and musician Paul McCartney.

"I accept ... there was considerable pressure on journalists at the News of the World to obtain stories to sell newspapers,"said the judge, John Saunders. "That may have led to a belief that the ends justified the means."

Edmondson is the eighth person from what was once Britain's biggest-selling paper to have been convicted of involvement in the widespread hacking of phones to find exclusive stories about politicians, celebrities, members of the royal family and others.

The scam was first uncovered at the paper in 2006, but Murdoch's British newspaper arm News International said then it was limited to its former royal editor Clive Goodman and private detective Glenn Mulcaire, who were both later jailed after admitting offences.

However the discovery of three emails sent from Mulcaire to Edmondson, then the paper's associate editor, at the end of 2010 led to a major new police investigation.

The emails, dating from 2006, provided instructions on how to hack the phones of the then deputy prime minister, a government minister and Frederick Windsor, the son of Queen Elizabeth's cousin.

Edmondson was sacked in early 2011 and the emails were handed over to police who slowly uncovered a huge scandal that ultimately led Murdoch to close the newspaper.

Edmondson originally denied the charges and was a defendant in a trial which led to the conviction and jailing in June of the paper's former editor Andy Coulson, who had later become Prime Minister David Cameron's media chief.

However he was ruled unfit to stand trial because of ill health. The trial was told Coulson had once instructed Edmondson when he was working on a story about a celebrity to "do his phone".