DJ Neil Fox – known as “Dr Fox” – has been arrested by police investigating claims of sex offences.
The arrest came after separate allegations were made by two women, the Metropolitan Police said.
The 53-year-old was held in Soho, central London, at the studios of Magic FM, where he presents the breakfast show. He was later released on bail.
Magic’s owners Bauer Media confirmed Mr Fox had been arrested and would not be presenting his show on Wednesday.
A spokesman said: “In the circumstances, Neil will be off air from tomorrow to enable him to devote his full attention to dealing with these matters.
“All other aspects of his contract will remain unchanged while matters are resolved. We can make no further comment at this stage.”
The Metropolitan Police confirmed a 53-year-old man had been arrested and taken to a central London police station. He has been released on bail pending further inquiries until early December.
The Met said four allegations of sexual assault had been made.
Three of the allegations have been described as historical but no time frame has been given.
One allegation is said to have taken place earlier this year.
Police said they had also searched properties in west London and the Littlehampton area of West Sussex.
Pop Idol judge
Mr Fox, who uses the nicknames Dr Fox and Foxy, began his career in local radio before moving to Radio Luxembourg and then London’s Capital Radio in the late 1980s.
He presented various slots there and in 1993, landed the job of presenting the Sunday afternoon Network Chart Show, later known as the Pepsi chart.
His big TV break, which brought him to a wider audience, was as a judge on ITV talent show Pop Idol between 2001 and 2003 alongside Simon Cowell, Pete Waterman, and Nicki Chapman.
Mr Fox later appeared in the BBC Three sketch show The Wrong Door.
He left Capital in 2005 and joined Magic 105.4, where he presents the breakfast show, Foxy in the Morning.
His arrest is not part of high-profile sex crime investigation Operation Yewtree, which was set up in the wake of revelations about BBC presenter Jimmy Savile.