UK police say they have saved more than 100 children from further abuse as a result of a two-year investigation into internet paedophiles.
Police say some Operation Ore paedophiles have re-offended
But senior officers say they need extra resources to combat convicted offenders who re-offend.
The compulsive nature of paedophiles' behaviour means new methods are needed to catch them, detectives say.
Operation Ore tracked down paedophiles worldwide who used credit cards to access pictures on a US website.
Senior detectives will be updated on an international investigation into child pornography on the internet at a briefing on Wednesday.
UK police checked more than 7,000 individuals identified by the inquiry.
In 102 cases there was evidence children in the UK had been abused so that pornographic images could be traded online.
In those cases the perpetrators have been arrested or the children found a safe refuge.
Jim Gamble, assistant chief constable of the National Crime Squad, told BBC Radio 4's Today programme: "We can name 102 children - clearly we won't - and can also name and link them to the actual abuser.
7,200 people identified
"We are talking about children from two years through to 14, 15 years of age who have been abused by individuals, sometimes known to them, sometimes in positions of trust like school teachers."
Latest figures show police in the UK arrested 3,537 Operation Ore suspects, making it one of the largest investigations carried out in the UK. Of those, 1,679 were charged and 1,230 convicted of offences.
Officers prioritised suspects already on the Sex Offenders' Register or who had direct access to children and painstaking efforts were made to ensure no-one was wrongly accused, Mr Gamble said.
"We are very conscious that if we make this kind of allegation against you today, we cannot simply wipe the slate tomorrow if we get it wrong," he said.
He said those charged were suspected of involvement in the "worst kind of hands-on physical abuse".
"As for the other people, they didn't get on to this site by accident," he said.
"You had to enter your credit card details, you had to go through a series of pages whereby you knew exactly where you were going and what you were going to see."
The achievements of Operation Ore were welcomed by Mary Marsh, chief executive of the NSPCC, who said it had helped prevent more children being abused.
"Behind every image is a real child who has suffered horrific abuse and every time an individual accesses an internet site to view images, they are creating a demand for more children to be abused," she said.
Ms Marsh called for more resources and better systems for assessing the risk posed to children by those caught downloading images.
"This has been a clampdown on just one site. There are thousands of children in the UK who are suffering sexual cruelty and have no-one to turn to, with images of their abuse being peddled on the internet every day."
Home Office minister Paul Goggins said the government was determined to do all it could to protect children from
paedophiles on the web.
"We believe that a picture of child pornography is a picture of child abuse,
and that sentences should reflect public concern on this issue."
The Sexual Offences Bill currently going through
Parliament would bring in measures to protect children and the most
vulnerable, he said.
Police say inquiries into two-thirds of the 7,200 suspects passed to them by the FBI are complete but there is still work to do.
And the BBC's Neil Bennett reports some men convicted as a result of Operation Ore continue to download paedophile material, sometimes using the same credit cards that led to their original arrests.
Senior police officers are lobbying for more resources and a new approach to tracking down offenders as a result.
Mr Gamble said: "What we need now is greater resilience and more funding for this type of policing activity."