Former News of the World editor Andy Coulson sent an email to a senior journalist at the tabloid ordering him to "do" a celebrity's phone, the trial over Britain's phone hacking scandal has heard.

Coulson, who later became Prime Minister David Cameron's media chief, denies conspiring to illegally access celebrities' voicemail messages in a scandal that forced Rupert Murdoch to shut the paper in 2011.

The trial heard that Coulson had been having an affair with fellow defendant Rebekah Brooks, his predecessor as editor and a close Murdoch confidante, for much of the time the pair are accused of involvement in hacking.

Prosecutor Andrew Edis said Coulson, as editor from 2003 until 2007, must have known his journalists were routinely hacking phones. "Does he know about phone hacking? He says he doesn't. We say: 'Oh yes, he did'," Edis told the court.


Prosecutors revealed Coulson's 1998-2004 affair with Brooks on the grounds that it showed they "trusted each other" and would have shared details about hacking.

In a letter found on Brooks' computer, dated 2004, she wrote to him: "I tell you everything, I confide in you."

Brooks was editor from 2000 until 2003 when Coulson, her deputy, took over. Having started as a secretary at the News of the World, she went on to become chief executive of Murdoch's British newspaper operations.

Coulson became Cameron's chief spin doctor in 2007 but was forced to resign in 2011 over persistent claims that he knew more about hacking than he had admitted.

Prosecutors argue Brooks, Coulson and the tabloid's managing editor Stuart Kuttner must have known about hacking because they were keeping an eye on its budget, and obtaining the information was expensive.