A child abuse investigation started two years ago by Kent Police has ended in a Canadian being jailed for three years.

Mark Bedford, a 22 year old student of Kingston, Ontario, used social networking sites to hack into the computers of 26 teenage girls in Kent.

Pretending to be a friend they knew, he persuaded the girls to undress and in some cases expose themselves. He then used the images to blackmail them further by threatening to send them to friends and family.

Following the investigation, Bedford was arrested and dealt with under Canadian law. He pleaded guilty to 10 charges relating to 75 counts including extortion, internet luring and making child pornography.

West Kent Chief Insp Tony Thomas said Kent detectives became involved in the investigation after receiving reports from the parents of a young girl who had been threatened on a computer social networking site.

He said: "This has been a complex investigation and jointly, with members of the Ontario Child Pornography Unit and other agencies in Canada, we identified Mark Bedford as the offender.

"I am pleased the case is now concluded and Bedford will serve a sentence behind bars."

Det Insp Steve Evans, one of the officers who went to Canada, said the investigation had unravelled "a huge, tangled series of unpleasant offences, being committed by the same person that spanned several countries".

He urged parents to think very carefully about letting children use computers unsupervised.