Simon Cowell
Music mogul Simon Cowell.

Simon Cowell has been unwittingly dragged into the drugs trial of N-Dubz star Tulisa Contostavlos.

In a dramatic turn of events, the court heard a secret recording where the former X Factor judge's personal assistant, Gareth Varey, told "Fake Sheik" Mazher Mahmood that Cowell was gay.

Mahmood, an undercover Sun reporter, posed as a wealthy film producer called Samir Khan when he met Contostavlos at London's Dorchester Hotel in May 2013.

The N-Dubz star is accused of acting as a fixer by introducing him to her friend Mike GLC who supplied the £860 worth of cocaine.

In the conversation that transpired off camera the reporter was heard asking Mr Varey if Cowell was gay, to which Varey replied: "Yes."

When Mahmood asked: "Have you slept with him?" Varey replied: "No."

Asked why, he answered: "I will when I make my move."

After Mahmood said: "How do you know he's gay?" To which Varey insisted that he knows people who had slept with him.

Giving evidence at London's Southwark Crown Court, Mahmood denied the defences' assertion that he manipulated Contostavlos by offering her a leading role in a Slumdog Millionaire-type film tipped for Oscar glory.

Under cross-examination Mahmood insisted he was not simply after a "sensational" world exclusive.

"The motive here is in the public interest to expose criminality," he said from the witness box behind a screen to protect his identity.

"Of course, I'm a journalist and stories are what I do for a living. That's not the reason I did it."

Contostavlos denies helping Mr Mahmood to obtain 0.5oz (13.9g) of the Class A drug.

The case continues.