The new generation of mobile video phones could make the huge scale of internet child abuse even worse, a report has warned.
A report by children's charity NCH, formerly National Children's Homes, said: "The internet is about to go mobile, and that could make many things more
difficult to prevent or detect.
"Almost all of the issues of child safety on the internet that exist today
become much more complex when the internet goes on the street."
Emerging 3G technology, likely to be widely available in the UK in the next year, gives users access to the internet, to see each other and to take, watch and send video clips.
John Carr, the author of the NCH report, said one of the problems with the phones was that people looking at child porn on the net were more anonymous than those using computers, who can often be traced.
He was particularly concerned about pre-paid phones - where a handset is bought without a contract and the calls are paid by voucher - as the retailer keeps no record of who buys them.
Mr Carr called on the industry to come up with a way that allows a "greater degree of certainty" about who is buying and using phones.
He was also concerned that with 3G phones, children could also be surfing the net away from the watchful eye of their carers.
Mr Carr said: "With the old, fixed internet, one of the cornerstones was
encouraging parents to supervise what their children did.
"That is far more difficult if children can get access to the internet from
anywhere by mobile phone."
Mr Carr called on mobile phone operators - who currently have a strong code about not marketing mobiles to children - to do more to educate them in the safe use of phones.
The phones also increase the opportunities paedophiles have to access sites which may serve only to fuel their fantasies.
And they could well make it easier for paedophiles to take and share images of children with others - or even to encourage children to take and send images of themselves, he said.
But the industry is well aware of these problems, and the six major operators - Hutchison 3G, Vodafone, Virgin, T Mobile, Orange and O2 - have begun working together to tackle them.
Hutchison's 3G network in the UK, 3, operates a "walled garden" approach, which means that users can only access internet sites approved by the operator.
Simon Gordon of O2 told BBC News Online: "It's something that we've been working on now for the best part of two years.
"We are taking it seriously and working with experts, child safety groups and the government on the best way to deal with this."
The six are due to publish a code of conduct in the next month, which covers various aspects of safety including filtration software, education and registration of users.
Mr Gordon said his firm was trying to tackle the points raised by Mr Carr.
It currently encouraged users to register their details, but could not force them to do so, he said - but if the government brought in a law to ensure all mobile owners were registered "we'd be happy to adopt that".
On education, he said his company had already begun to talk to children directly, with teams of staff touring schools and talking to pupils.
Hints and tips included "don't use camera phones outside the school gates", and "tell a teacher or other adult if anyone you do not know tries to contact you over your phone," he said.
The companies said they were also working on barring unsuitable content which children could be upset by, or which could help paedophiles desensitise and "groom" children.
Al Russel, head of content at Vodafone UK, said his firm wanted people to have to make a special effort to view adult material - and children to be unable to do so.
"At Vodafone we're pursuing a policy of if you're not 18, you can't see any 18-rated content.
"So if you want to see 18 content, you'll have to register a credit card, or go into a retail shop to make these services available," he said.