Dane Bowers was quizzed by cops on Tuesday and arrested on suspicion of conspiracy to rape, according to a report.
A woman claimed she was attacked in a hotel room in the early hours of Saturday, shortly after the former Another Level star, 32, headlined a DJ set at the Deco Lounge nightclub in Hertford.
She later contacted police and detectives took a video statement from her.
Dane, who appeared on Celebrity Big Brother in 2010, attended Hatfield police station on Tuesday by prior appointment and was subsequently arrested, reports The Sun.
The singer was accused of conspiracy to rape, while his friend was quizzed on suspicion of rape, claims the newspaper.
A spokesperson for Hertfordshire Police says: "A 32-year-old man from Surrey presented himself at Hatfield police station by prior arrangement on April 3.
"The man has been arrested and is assisting police following an allegation of sexual assault."
Dane and his 35-year-old friend reportedly deny the allegations and were bailed until 14 May.