By Martin HickmanAndy Coulson today denied telling his long-time lover and fellow redtop journalist Rebekah Brooks that he was about to confront a Cabinet minister over an affair.The former News of the World editor told the phone hacking trial that he would not share an exclusive with Mrs Brooks, editor of its daily sister The Sun, because they edited "rival newspapers."Mr Coulson has said that while editing the NoW in 2004 he was told by the paper's chief reporter that the Home Secretary, David Blunkett, was having a relationship with a married woman.He said he knew Mr Thurlbeck had "hacked" Mr Blunkett's messages before confronting the politician about the relationship in an attempt to stand up the story. Mr Blunkett recorded the meeting with Mr Coulson at his Sheffield constituency, and the tape was played to the jury last week.Giving evidence for the third week, Mr Coulson said he did not tell the Home Secretary that his messages had been intercepted because it would aggravate a potential privacy problem with the story and make it seem more aggressive.He said he needed to ask Mr Blunkett about the relationship because he could not be sure that it was true.Andrew Edis, QC, for the Crown, suggested that by not revealing that he knew the story was correct because of the hacked voicemails, Mr Coulson was "lying" to the Home Secretary."I wouldn't say I was lying to him," Mr Coulson replied."I would say I was trying to get the story stood up... I thought it was most likely to be true, but that's very different to true."Mr Edis countered: "You told him: 'I know that this is true' - and your evidence is that you didn't know it as true.""I accept that I was being disingenuous," the journalist replied.Intervening, Judge John Saunders asked: "Were you telling a deliberate untruth: yes or no?"After a pause, Mr Coulson replied: "Yes."He also accepted: "I was being disingenuous about the sourcing of the story," when he told Mr Blunkett that he had "sources" rather than a single source: the hacked messages.Phone records show that Mr Coulson and Mrs Brooks spoke several times before he confronted Mr Blunkett.Mrs Brooks' Sun revealed the identity of the woman for whom Mr Blunkett had been leaving messages, the day after Mr Coulson's News of the World revealed the affair.Mr Edis asked: "Did you tell her what you were doing?", to which Mr Coulson replied: "I don't believe I did, no."Surely he was not worried that the woman who had written him a long love letter the year before about their relationship "would spoil it for a story?", the prosecutor inquired.Mr Coulson replied: "No, there was a closeness between Rebekah and I but that did not extend to sharing one another's exclusives. There was a line drawn. We were editors of rival newspapers."Mr Coulson, editor of the NoW between 2003 and 2007, and Mrs Brooks, editor of the NoW between 2000 and 2003 and editor of the Sun between 2003 and 2009, deny conspiring to hack voicemails. The case continues.