A DANGEROUS internet predator who preyed on hundreds of young girls bore “chilling similarities” to the murderer of North-East teenager Ashleigh Hall, police said last night.

Click here read about the tragic case of Ashleigh Hall

Dennis Forster used online chatrooms and social networking sites such as Facebook to contact and befriend his victims and try to draw them into prostitution and pornography.

When they refused his requests and demands for meetings, the Stockton security guard threatened to murder their families, burn down their homes and sell them for sex.

As Forster began an indefinite prison sentence last night, Andrea Hall, the mother of Darlington teenager Ashleigh, who was murdered by loner Peter Chapman two years ago, called on authorities to do more to safeguard children using the web.

“What happened to Ashleigh is still happening,” she said. “There’s got to be some way of checking who these people are when they go online.”

The terms of Forster’s prison sentence mean he may never be released after he admitted a catalogue of offences branded “disturbing in the extreme” by police.

Judge Howard Crowson, at Teesside Crown Court, imposed a sentence of imprisonment for public protection (IPP) after hearing the 27- year-old claim he could not remember what he had done.

He said he rejected entirely Forster’s suggestion that his heavy drug-taking made him unable to recall grooming the girls over a three-year period.

“This was a display by you of a propensity to act in a premeditated and calculated manner for an extensive period of time, and you were fully aware of your offending behaviour.

It is clear you are a man who preys upon teenage girls,” the judge said.

“You continue to pose a high risk of harm which, in my judgement, is unmanageable in the community.

“It is inconceivable you could have carried out this level of persistent, detailed, skilful manipulation while at the same time being any way incapacitated by the use of drugs.”

Detective Constable Stuart Hodgson, of Cleveland Police, said after the hearing that he believed Forster would have gone on to commit more serious crimes had he not been caught earlier this year.

He said there were chilling similarities with the case of Ashleigh Hall, who met paedophile Chapman over the internet.

“I have no doubt that had we not been made aware of Forster when we were, we would have become aware of him within a year for more serious things,” said Det Con Hodgson.

“It was definitely his intention to meet these girls and if we had not apprehended him when we did, it could well have been a very different story at a point further down the line.”

The mother of one victim, from Teesside, said: “The case highlights the need for all parents to remain vigilant.

“It’s neither the children nor the sites that are to be blamed, but the predators such as Forster who utilise them for their own depraved purposes.”

Mrs Hall echoed the mother’s comments, but added: “What’s it going to take for them (Facebook) to do something?

Ashleigh’s been gone for two years now and Facebook’s got bigger and bigger in that time with more people joining.

How do we know who they all are?”

The Child Exploitation and Online Protection Centre’s (CEOP) head of education, Jonathan Baggaley, said children needed to be aware that some people on social networking lied about who they were. He added: “It’s important to trust your instincts – if something doesn’t feel right, it probably isn’t.”

He urged users to contact CEOP via the ClickCEOP button at ceop.police.uk if they had concerns about someone they were talking to. Users can also get advice and guidance at facebook.com/clickceop The court had heard how the balding loner incited girls – all aged between 12 and 15 – to have sex with him, allow him to carry out other acts and, in one case, sleep with his friends.

The 11 victims were just a small sample of those from all over the country who were targeted by Foster, said Anthony Moore, prosecuting.

He told one of the schoolgirls -– aged 14 – in a message on her Facebook page: “Can’t wait for you to turn 16. We can be Mr and Mrs Dennis Forster and make a bump together.”

Forster incited four of the girls to involve themselves in pornography by taking pictures of themselves and sending them to him, or by recording images on a camera and DVD; He incited one girl to become a prostitute, threatened to kidnap one and sell her for sex, and warned he would kill another’s parents if she did not appear naked over a webcam.

The court heard that he threatened to take her away from her family, and vowed to burn down or bomb the home of another girl’s parents because she had spoken to police.

When Forster was arrested at his home in Corporation Street, police found dozens of indecent videos and photographs of children, and some extreme adult pornographic images.

He admitted 22 charges of inciting a child to engage in sexual activity, inciting child pornography, inciting child prostitution, making indecent photographs of children, possessing extreme pornographic images, possessing a prohibited weapon – a CS gas canister – and intimidation.

His barrister, Stephen Constantine, said it was an important feature of the case that Forster did not physically harm any of the children, but said he had to accept that some of the girls were threatened into doing things.

The barrister described Forster as “something of a loner who almost shunned contact with the outside world”

and said: “Within his own little world, it appears no small degree of fantasising has taken place. Whether that’s what this case is about it is difficult to say.”