Former News of the World editor Andy Coulson allegedly used "phone hacking, surveillance and confrontation" in an attempt to confirm a bogus tip about an affair involving then-home secretary Charles Clarke.
Prosecutor Andrew Edis QC told the Old Bailey that the News of the World (NotW) heard a false rumour in May 2005 that Clarke was seeing his "attractive special adviser", Hannah Pawlby.
The newspaper tasked private investigator Glenn Mulcaire with hacking Pawlby's voicemails and "door-stepped" her, but Coulson also called and left her voicemails, the court heard.
"The prosecution suggests that Mr Coulson, who is now the editor of the NotW, he is not the man who stands outside people's houses hoping to catch them out, he is the man who likes to put the story to people to see what they will say," Mr Edis said.
He said the NotW used three ways to investigate stories: phone hacking, surveillance, and confrontation.
"The editor is personally involved in the third. Obviously he knows about the second, surveillance, he must do. What about the first? Does he know about phone hacking? He says he doesn't, we say `Oh yes, he did'."
Rumours about an affair involving Clarke were first picked up by the NotW's features desk when a source who was sexually interested in Ms Pawlby was told: "Don't bother wasting your time, she's with Charles."
A tape of voicemails taken from her phone on at least three occasions was seized from Mulcaire's home in August 2006.
Investigators also found entries on the private investigator's computer which had Ms Pawlby and her sister as "Projects".
During the period she was being investigated, Ms Pawlby's grandparents received anonymous calls asking for information about her, Mr Edis said.
Meanwhile, former chief reporter Neville Thurlbeck and former reporter James Weatherup oversaw surveillance of Ms Pawlby's movements.
Leaving her a voicemail on June 18 2005, Coulson told her: "I've got a story that we're planning to run tomorrow that I really would like to speak to Charles about."
Mr Edis said Coulson's involvement in the story followed the same pattern as with other important men, such as former home secretary David Blunkett.
The jury heard on Thursday that Coulson confronted Mr Blunkett over an affair with a married woman while he was himself seeing co-defendant Rebekah Brooks, who was married at the time.
Coulson and Brooks deny conspiring with others to hack phones between October 3 2000 and August 9 2006.Mulcaire, Thurlbeck and Weatherup have admitted phone hacking.