There’s a surprising twist in the ongoing child custody battle between R&B crooner Usher Raymond and his ex-wife, struggling celebrity stylist, Tameka Foster. The NY Post reports that Foster’s attorneys have demanded that Usher submit to a drug test as part of his response to her petition to strip him of his parental rights to their two sons.

But, according to The Post, Usher flatly refused to take the drug test. Foster’s court documents indicate that a drug test was demanded, in part, because of blog rumors that Usher is a well-known nose candy connoisseur.

The custody battle between Usher Raymond and his ex-wife, Tameka Foster, is turning to war: Justin Bieber mentor Usher last week rejected a demand by his ex to submit to drug testing after she alleged he was “in delirium” during a January concert in Germany.

She also filed a request for Raymond to submit to drug testing, claiming she found mysterious pills in his jeans pockets in September 2008, and that she believed he was wasted during the Germany concert, according to court documents.

Video circulated widely online at the time showing Usher meandering onstage in front of the crowd and unable to sing. He apologized to fans, and his reps blamed a respiratory infection for his inability to perform.

Foster, however, alleges he was under the influence of something. “I dated him . . . when he’s had a very serious throat condition and he still performs like a champ,” she said. “ I really feel strongly that something was going on there, and it wasn’t, ‘Oh I have laryngitis.’ ”

She made a further claim in the deposition: “I believe he gets high. And if he doesn’t then he’d take the drug test, correct?” Source