A telephone sex pest who is believed to have connections with Oxfordshire has struck again.

The man, who has made more than 200 calls in the past four years, targets young boys and girls, aged 14 and 15.

In some calls, he has claimed to be carrying out a survey for a radio station in Oxfordshire called Radio Fox.

Police have spoken with Fox FM and eliminated all Fox FM staff from the inquiry.

The man offers incentives, such as CDs, to his victims to get them to take part and begins by asking basic questions, such as name and age but the tone soon becomes sexual.

The calls, which have been made to teenagers living in the Darlington area of County Durham, are normally made to home numbers.

However, calls have also been made to public phone boxes and the man has asked for the names and phone numbers of victims' friends.

Pc John Milburn, who is leading the investigation, said the man had struck again earlier this month, after a break of almost two years.

He said the man sometimes used public phone boxes and mobile phones.

He is also believed to use the Internet to connect with phone exchanges in America, which makes the calls untracable.

Pc Milburn said: "We believe this man has knowledge of the Oxfordshire area, and may have friends there."

He added that the man may use CDs which list names, addresses and ages of people to target his victims, as well as information given to him by teenagers about their friends.

Anyone with information is asked to call Pc Milburn on 01325 742124.