Tom Stephens, a supermarket worker from Trimley St Martin, near Felixstowe, Suffolk, has been arrested on suspicion of murdering five prostitutes in Ipswich.
In an interview with Mr Stephens, conducted by BBC reporter Trudi Barber last week, he said he had befriended some of the murdered women because he was "very sad and very lonely and obviously I wanted sex because I was paying for it".
Mr Stephens requested that the interview was used for background purposes only and that it was not intended for broadcast. Subsequently, a copy has been made available to the police.
Mr Stephens said he had known Gemma Adams for 18 months and Tania Nicol for six months but said he had become closer to Miss Nicol. He described himself as "the closest thing Tania had as a boyfriend", adding that "neither of us were faithful to the other one".
Mr Stephens, who says on his page on the social networking website MySpace that he studied at Thorpe St Andrew School in Norwich, said he also knew their fellow prostitute Annette Nicholls - who was also murdered.
He said he had not known another of the murdered women, Anneli Alderton, "at all" before her disappearance.
"I didn't know Anneli at all. I've only ever spoken to her since both Tania and Gemma went missing," he said.
It had been "partly to say, if you know anything, please talk to the police and if you won't talk to the police, please talk to me and I'll talk to the police", he added.
Mr Stephens said he was particularly close to Tania Nicol
"And also trying to say, 'Are you okay?'," he said.
"Pretty much all the girls who I didn't know before, I've tried to speak to since in that way."
Mr Stephens, who says on his MySpace web page that he is a team leader at a Tesco supermarket having worked there since 1997, said he enjoyed friendships with "a number of the girls" working in Ipswich as prostitutes.
He said: "I wanted to chat with the girl, before and after [sex], which is partly why I was always happy to give them a lift.
"They'd quite often want a lift to get their drugs and I would give them a lift and it was better for me like that and that's how it developed into a friendship with a number of the girls."
Mr Stephens denies any wrongdoing.