Glenn Mulcaire blagged MP Mark Oaten’s mobile phone details before the News of the World paid the politician’s gay lover £20,000 for details of the affair, a court heard.
Andrew Edis QC for the prosecution told the jury that Oaten was involved with a young man in January 2006 when the News of the World became aware of the affair.
Edis told the jury: “Mark Oaten was a candidate for the leadership of the Lib Dem Party, but at that time the newspaper detected a relationship between between him and a young man, Ian Chadwick.
"Mr Oaten was married at the time – he may still be married today, I did not mean to imply anything by that – and the newspaper eventually got the story by paying Mr Chadwick £20,000."
Edis told the jury that Muclaire “blagged” Oaten’s phone details from Vodafone before hacking his voicemail ten times.
Mulcaire has already pleaded guilty to phone-hacking.
The prosecution alleges that several senior News of the World staff and executives were involved in a conspiracy to hack the mobile phones of a range of high profile people.
Former News International chief executive Rebekah Brooks, 45, of Churchill, Oxfordshire (pictured above); ex News of the World editor Andy Coulson, also 45, from Charing in Kent; former NoW head of news Ian Edmondson, 44, from Raynes Park, south west London; and the tabloid's ex-managing editor Stuart Kuttner, 73, from Woodford Green, Essex, are all on trial accused of conspiring with others to hack phones between 3 October 2000 and 9 August 2006.
Former NoW and Sun editor Brooks is also accused of two counts of conspiring with others to commit misconduct in public office – one between 1 January 2004 and 31 January 2012 and the other between 9 February 2006 and 16 October 2008 – linked to alleged inappropriate payments to public officials.
She faces another two allegations of conspiracy to pervert the course of justice – one with her former personal assistant Cheryl Carter, 49, from Chelmsford in Essex, between 6 July and 9 July 2011; and a second with her husband, Charles Brooks, and former head of security at News International, Mark Hanna, and others between 15 July and 19 July 2011.
Coulson is also facing two allegations that he conspired with former NoW royal editor Clive Goodman, 56, from Addlestone in Surrey, and other unknown people to commit misconduct in public office – between 31 August 2002 and 31 January 2003, and between 31 January and 3 June 2005.
All of the accused deny all of the charges.
The trial continues.