LONDON (REUTERS) - British Prime Minister David Cameron's ex-media chief Andy Coulson will face a re-trial over whether he sanctioned illegal payments to a public official while editing a Rupert Murdoch tabloid, prosecutors said on Monday.

Last week a jury at London's Old Bailey failed to reach a verdict on whether Coulson and the News of the World's former royal editor Clive Goodman were guilty of making illegal payments to a police officer to obtain telephone directories for Britain's royal family.

Coulson was however found guilty of conspiring to hack into voicemail messages to generate front-page news at the now defunct Sunday tabloid and he is likely to be sentenced later this week.

Three other journalists and a former investigator from the mass-selling paper also pleaded guilty before the trial began and they will be sentenced along with Coulson. "For a period of years there was industrial scale phone-hacking at the News of the World," prosecutor Andrew Edis said at the opening of the sentencing hearing.

The 46-year-old Coulson had edited the now defunct Sunday tabloid between 2003 and 2007. He stepped down after Goodman and the private investigator admitted hacking into phones to generate front page news stories.

Just months later he went to work as the communications director for Cameron, first in opposition and then in Downing street when the Conservative leader was elected as prime minister in 2010.