Police analysis of computers reveals that, before befriending a child they intend to groom for online abuse, perpetrators often research the victim's location, school and other details, so as to present a convincing picture of themselves as a local young adolescent.
Children as young as 8 are being targeted, according to the centre. Such grooming often starts on open chat forums before moving to private areas where the talk swiftly becomes more explicit.
The threats usually start after children have been tricked into posting compromising pictures of themselves that they fear could be distributed more widely.
In one online conversation retrieved by the authorities, an abuser tricked his victim and then became increasingly aggressive, saying he did not care if the boy killed himself. "I totally own you," he said.
The practice appears to be a new, more menacing development in the world of cyber-bullying. Children have been forced to film themselves on webcams as they write degrading statements on their bodies or cut themselves, says the centre.
One abuser collected images of his blackmailed victims in a folder named "slaves". A British teenager is one of seven young people who have killed themselves over blackmail.
Daniel Perry, 17, of Dunfermline, Fife, leaped from the Forth Road Bridge in July. He had been having online chats with a person he believed to be an American girl of his own age, but was then told his conversations would be played to his family and friends unless he paid money into a bank account. Police are still investigating Daniel's death.
Experts said that, while they had seen a few cases of extortion, most blackmailers were motivated by sexual desire and sadism. "There is a desire for power and control, and getting a kick out of causing as much pain as possible," said Dr Elly Farmer, a clinical psychologist.
The child exploitation centre has had 12 operations over the past two years in which the blackmailing of children into performing sex acts was a clear motive, with 424 victims worldwide and 184 in Britain. Five of those operations - against groups and individuals - were in Britain. The centre said the number of victims identified represented a small fraction of the number targeted.
The global nature of the problem was highlighted by "Operation K", launched this year after a complaint by one victim to police in Britain. It revealed evidence of a group of friends in an unspecified country acting together to ensnare young children. They operated dozens of profiles and email addresses on five websites.
Most of the British children targeted were boys aged 11 to 15.
Britons were disproportionately targeted because they spoke English, and in the apparent belief that liberal values in this country were likely to make them more susceptible to online grooming, the centre said.
Many of the victims were forced to conduct graphic sex acts. "The coverage was immense," said the centre's operations manager, Stephanie McCourt. "It was very easy for children to get caught up in that process."
A group of men, aged 20 to 44, are due to go on trial within the next month in an unspecified non-European country that authorities declined to name for legal reasons.
The centre said a third of its operations had seen abusers operate on the so-called "Darknet" - an encrypted sub-layer of the world wide web that is supposed to ensure anonymity - but officials said people were arrested in every "sting". They declined to say how suspects were identified. "Young people must remember that the online world is the real world. Pictures can be distributed to thousands of people in seconds and can never be fully deleted," said John Cameron, the head of the National Society for the Prevention of Cruelty to Children helpline.
"We need to educate young people but also reassure them that no matter what threats people make to them over the internet, they can be stopped and the crime they are committing is very serious and can result in a lengthy jail sentence."
Last year, two brothers in Kuwait were jailed for five years after targeting 110 children around the world.
- Independent
