Four members of a nationwide child sex ring who swapped sick images via an internet group have been jailed for a total of seven years.

Police said the on-line group contributed to "horrific sexual abuse' of children.

David Adams, 45, of Hinton Waldrist, between Oxford and Faringdon, admitted 17 offences of possessing and distributing indecent images of children.

He was sentenced to 15 months in jail at Oxford Crown Court on Monday.

Adams joins three other members of his on-line child porn group including Carl Rogerson, 36, of Cholswell Road, Abingdon, who is in jail for three years after admitting 26 similar offences in May.

Darren Hawkins, 38, from Broome Way, Banbury, pleaded guilty to 26 offences and was sentenced to 21 months imprisonment in April.

A fourth member of the sick internet group, Shaun Smith, 45, of Barn Crescent, Newbury, pleaded guilty to 20 offences at Oxford Crown Court on Monday and will serve one year in jail.

The four men were uncovered following a complex nationwide investigation including officers from the Thames Valley Police High Tech Crime Unit.

They were part of an on-line chat group which dealt in child abuse images and discussed sick fantasies.

Det Sgt Duncan Wynn, from the High Tech Crime Unit, said: "The seriousness of these offences is clearly reflected in the sentences passed to these four offenders.

"Clearly by sending and receiving these images, they contribute to the demand for this kind of material, which results in children being subjected to horrific sexual abuse.

"The success of this operation sends out a clear message that, despite offenders using more sophisticated methods to avoid detection, we will track them down and they will be brought to justice."