The man, who was arrested on suspicions of murdering five prostitutes in Suffolk, used to be a voluntary police officer, Sky News reported.
Tom Stephens, 37, a supermarket worker, also worked as a part-time taxi driver.
He was arrested this morning at his home in Trimley, a small town near Felixstowe, Det Chief Supt Stewart Gull said.
Stephens was interviewed by the Sunday Mirror yesterday.
He told the newspaper he knew the girls well, had been interviewed by police four times but was completely innocent.
"I'm not worried about being charged - I am innocent," he said.
Former prostitute Jacci Goldsmith told Sky News that Stephens looked after the women on the street.
"I am shocked, he would help us whenever he could," she said.
"He was quite well known. He would come out nearly every night. They just had to phone him up and if he could he would come out and take us to where we wanted to be.