DJ Neil Fox - known as "Dr Fox" - has been arrested by police investigating claims of historical sex offences.
The arrest came after separate allegations were made by two women, the Metropolitan Police said.
According to reports, the 53-year-old was arrested in Soho, central London, at the studios of Magic FM, where he presents the breakfast show.
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."
Police confirmed a 53-year-old man had been arrested and said he was still in custody in a central London police station.
They 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 in 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.
He 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.