The judge in the trial of Tulisa Contostavlos told the jury there were "strong grounds" to believe an undercover reporter had "lied" at a hearing before the trial began.
Judge Alistair McCreath was speaking as he threw out the case at Southwark Crown Court.
The Sun's Mazher Mahmood - known as the 'Fake Sheikh' - had posed as a wealthy film producer when he met Contostavlos at a number of hotels and restaurants.
The former N-Dubz singer strongly denied that she had helped broker a drug deal between Mahmood and her rapper friend Michael Coombs, also known as Mike GLC.
More top news
David Cameron has admitted the General Election is on a "knife-edge" as he tried to woo voters with the promise of a "truly seven-day" NHS.
It's shaping up to be a windy weekend with spells of rain. However we will see some dry and bright spells too.
Two murderers who wed in Britain's first gay prison marriage will not be allowed to share a cell.