The drug trial of a former British "X Factor" judge collapsed on Monday after the judge said the star prosecution witness, an undercover reporter known as the "Fake Sheikh," had lied under oath.
The Rupert Murdoch-owned Sun on Sunday tabloid reported last year it had caught Tulisa Contostavlos acting as go-between in a deal to sell cocaine to a reporter posing as a film producer.
The scoop was the work of Mazher Mahmood, a journalist famed for pulling off undercover stings while disguised as a wealthy Arab businessman.
Contostavlos was charged with supplying drugs, but judge Alistair McCreath stopped her trial Monday, saying there were "strong grounds to believe" Mahmood had lied in court.
The judge said a chauffeur named Alan Smith had been expected to testify that Contostavlos had told him she disapproved of drugs — "but after (a) conversation with Mr. Mahmood, he had changed his mind." At a pre-trial hearing, Mahmood denied speaking to Smith about the issue.
McCreath formally acquitted Contostavlos, who had pleaded not guilty, and co-accused Michael Coombs, also known as rapper Mike GLC.
Contostavlos, 26, gained fame as part of London music group N-Dubz before a stint as a judge on TV talent show "The X Factor."
Outside court, Contostavlos accused Mahmood of "horrific and disgusting entrapment." She said she had believed she was auditioning for a role in a major movie, with Leonardo Di Caprio as a potential co-star.
"Mahmood got me and my team completely intoxicated and persuaded me to act the part of a bad, rough, ghetto girl," she said. "They recorded this and produced this as evidence when I thought it was an audition."
The Sun said Mahmood had been suspended pending an internal investigation.
Mahmood became famous — and feared — for celeb-trapping stings during a long career at the now-defunct News of the World. His targets have included ex-England football coach Sven Goran Eriksson, Princess Michael of Kent and Prince Edward's wife, the Countess of Wessex.