Up to 100,000 people may be involved in downloading child pornography in Britain, a senior West Midland Police Officer has warned.
But the internet has actually made it easier for police to catch paedophiles, said Detective Sergeant Damian Morgan.
He was speaking following the revelation last week that arrests and convictions for internet child porn offences have more than quadrupled in just two years
New figures showed 2,234 people were cautioned or charged with crimes in England and Wales in 2003, compared with 549 in 2001.
The increase was put down to arrests following Operation Ore, which identified around 7,000 British customers of an American website selling access to child pornography.
West Midlands Police has one of the UK's largest police units dealing with high-tech crime and paedophiles.
It analyses computers which have been seized from suspects to determine whether they have been used in crimes including downloading child pornography.
It also deals with specific cases referred to it, often by worried parents concerned their child has been approached by a paedophile.
Det Serg Morgan said: "We have had cases where parents have picked their child's phone up to find someone suspicious on the other end, or have seen that their child is receiving suggestive text messages."
However the force has its hands full dealing with the cases referred to it and rarely has the capacity to seek out paedophiles.
"Unfortunately, if we did that we could target 20 to 30 people a day, every day.
"Operation Ore was 7,000 subjects in the UK. But we know there are well in excess of 100,000 people downloading indecent images of children."
He said there was a need for more research into the scale of paedophilia and the causes of it.
The internet had helped paedophiles make contact with each other and form networks of people sharing images, he said. But it also helped police to catch them.
"Children very rarely report incidents of abuse. It has usually been adults reporting something that happened in the past.
" That meant we were arresting people who were in their 40s or 50s or older. They were entrenched in their behaviour and often had many victims.
"The internet allows us to target them better, and we are arresting them at a much younger age."
Children's charity NHC last night called for Internet companies to block access to child pornography.
John Carr, the charity's Internet Safety Advisor, said: "Child pornography on the internet is a modern curse and ISPs have a critical part to play in stamping it out."
He added: "These new and astonishing numbers reflect the arrests made during Operation Ore."
Between 2002 and 2003 the figure - compiled by the Home Office - rose from 870, a year-on-year rise of 157 per cent, said the charity.