A PAEDOPHILE posed as a 13-year-old girl on the internet to prey on other youngsters and try to arrange meetings so he could abuse them.

But Anthony Nelson became the victim of a double-bluff - because one of his targets was really an undercover police officer pretending to be a child.

Nelson, 51, from Shildon, County Durham, is now facing a lengthy prison sentence after pleading guilty to a string of sickening charges in court.

Police last night warned of the dangers of social networking sites and again called on adults to carefully monitor what their children do on-line.

Twice-married Nelson was arrested in January when it emerged he had contacted an 11-year-old girl through a false Facebook account he had set up.

Pretending to be a 13-year-old, he slyly gained the confidence of his victims and persuaded some of them to send him their mobile telephone numbers.

The depraved dad then began engaging in sexually explicit text messages with the youngsters - some still at primary school - and tried to set up meetings.

What bearded and bespectacled Nelson did not know was that one of his intended victims was in fact an undercover officer from Durham Constabulary.

A concerned parent had alerted the police about the Facebook messages sent to their own child - and detectives discovered there were many more.

An examination of Nelson's computer showed he had contacted dozens of children all over the country over six months - including many in the North-East.

Where possible, police have spoken to the parents of the youngsters and to schools to tell them what the former hotel night porter had been up to.

The balding pervert admitted making and possessing pictures of child abuse and bestiality, and inciting children to engage in sexual activity.

With his head bowed and through occasional sounds of sobbing, he also pleaded guilty to trying to arrange a meeting with a girl to commit a sex crime.

He was remanded in custody and will return to Teesside Crown Court later this month to be sentenced after background reports have been prepared.

Detective Constable Jonathan Stoker, who investigated the case, said last night that he had preyed on his victims' nativity in a sickening way.

He told The Northern Echo: “Nelson has taken advantage of young children, some of whom were still in primary school, to fulfil his sexual desires.

"While I have been speaking to some of the families affected by this case, one parent commented that 'it was like he had been in their house'.

"I would encourage parents and carers to make sure that if a child is part of a social network like Facebook, to check the account settings and to make sure it is as private as possible.”

Nelson, of Redworth Road, admitted two charges of causing or inciting a child to engage in sexual activity and attempting to arrange the commission of a child sex offence.

He also pleaded guilty to 17 counts of making indecent images of children, possessing 1,384 such images and possessing extreme pornography.

His barrister, Carl Swift, told Judge Peter Bowers that Nelson hoped to be sentenced straight away but his probation report had not been prepared.