Image caption Mazher Mahmood and Alan Smith both deny intending to pervert the course of justice

Undercover journalist Mazher Mahmood plotted to change a witness statement in a case against pop singer Tulisa Contostavlos, the Old Bailey has heard.

The reporter known as the Fake Sheikh and his driver Alan Smith both deny conspiring together, intending to pervert the course of justice.

Miss Contostavlos had been accused of supplying cocaine but the case against her collapsed in 2014.

Prosecutors said Mr Mahmood had had a "vested interest" in her prosecution.

The court heard that Miss Contostavlos had been targeted by the self-styled "king of the sting", who posed as an influential film producer who wanted the singer to star in a Hollywood blockbuster.

X Factor judge

The singer had allegedly arranged for Mr Mahmood to be sold half an ounce of cocaine by one of her contacts for £800.

The former N-Dubz star and X Factor judge was later arrested and charged with being concerned in the supply of a class A drug, after Mr Mahmood handed evidence to police.

Mr Mahmood, 53, of Purley, south London, and Mr Smith, 67, from Dereham, Norfolk, are accused of arranging to alter a written statement the latter had made to police because it was favourable to Miss Contostavlos's defence.

Image copyright Getty Images Image caption The pair are accused of plotting to change a witness statement in the case against pop singer Tulisa Contostavlos

Opening the trial against Mr Mahmood and Mr Smith, Sarah Forshaw QC told the jury: "In effect, the hearing in June 2014 put Mr Mahmood and his journalistic process on trial.

"He liked to call himself the king of sting, he boasted in a book he had written of the number of convictions that he personally was responsible for.

"He knew that if it could be shown that he had acted improperly as an agent provocateur, inducing Miss Contostavlos to do something she would not otherwise do, his own credibility and standing and the prospect of conviction in the case might both be severely damaged."

Miss Forshaw added: "Miss Contostavlos had expressed her disapproval of hard drugs to his own driver, that was the bit of the statement that was altered.

"Mr Smith had told the police officer making the statement that he remembered that while driving Miss Contostavlos... that she had spoken about someone in her family being dependent on cocaine."

'Texts and calls'

Mr Smith had told a police officer she seemed really negative about cocaine but, a day later, he told police he wanted to retract that part of his statement, the court heard.

It is alleged that in the intervening 24 hours Mr Smith had sent a copy of his interview to Mr Mahmood and they had exchanged a number of texts and calls.

Image copyright PA

During a pre-trial hearing at Southwark Crown Court in June 2014, Mr Mahmood said on oath that he had not spoken to Mr Smith about Miss Contostavlos's comments.

"He deliberately misled the court - not only had he discussed it but he had been sent a copy of the statement," Miss Forshaw said.

When later giving evidence to the jury in the case, Mr Mahmood admitted he had seen a copy of Mr Smith's statement and Miss Contostavlos's trial subsequently collapsed, she added.

Miss Forshaw told the jury: "There is no doubt that Smith did change his statement...

"The change would undoubtedly have disadvantaged Miss Contostavlos's case. It would have deprived her of supporting evidence from Mahmood's own right-hand man that she made an anti-drugs comment at a time when untainted by any influence or pressure."

She said the evidence in the case was "overwhelming", adding: "Mr Mahmood may be the master of subterfuge and deception. But on this occasion it is he, together with his employee, who are exposed."

'Drunk'

The jury also heard Miss Contostavlos describe how she was tricked by Mr Mahmood after meeting him at the Metropolitan Hotel in Park Lane, London, in May 2013.

In a statement read to the court, she said she could not fully remember the events because she was "drunk".

Miss Contostavlos said Mr Smith had later driven her home and she had talked about an unnamed member of her family with a "hard drug problem".

Mr Mahmood and Mr Smith are charged with conspiring together to do an act, namely that Mr Smith would change a draft statement to police, with the intention to pervert the course of justice, between 22 June and 22 July 2014.

Both deny the charges. The trial continues.