Five-year-old April Jones was abducted and murdered in rural Wales last October by convicted pedophile Mark Bridger. During his trial, it emerged that Bridger had searched online for images of child abuse and rape before carrying out the killing.

In a separate case, 12-year-old Tia Sharp was murdered last August by a man close to her family, Stuart Hazell. Hazell was also found to have searched the internet for pornographic websites, pursuing a growing interest in child sex abuse images.

These two cases have led to growing calls in the UK to block access to images of child pornography. Child pornography is illegal in the UK. John Carr, who advises the government on child Internet safety, has called publicly on search engines to do more to tackle the issue.

"If you're sufficiently determined there's no doubt you can get to [these images] - it's six or seven clicks," Carr told DW.

It's already the case that searching for terms such as "child rape" on a search engine will not directly call up links to illegal images. But they may provide a gateway to hardcore adult porn sites, which often have coded links to other material, using words such as "teen" or "barely legal."

Calls for changes to search settings

Carr proposes that internet companies should block all links used by pedophiles to find images of child sexual abuse.

He adds that search engines should set their default settings to the safest option - which blocks access to legal as well as illegal sex sites.

Under his proposal, those wanting to access pornographic material would have to register and to prove that they were over 18 years of age. Given that users would have to reveal their names, Carr believes this lack of anonymity would deter people from accessing illegal images.

"And that one thing, on its own, without more, would do a huge amount to deter a lot of guys from getting into child pornography at all in the first place," says Carr.

Support from search engines

The big search engines say they cooperate closely with governments and NGOs to clamp down on illegal images. In a statement, Scott Rubin, director of communications and public affairs at Google, told DW:

"Google has a zero-tolerance policy on child sexual abuse content. We are members and joint funders of the Internet Watch Foundation - an independent body that searches the web for child abuse imagery and then sends us links, which we remove from our search index. When we discover child abuse imagery or are made aware of it, we respond quickly to remove and report it to the appropriate law enforcement authorities."

Jon Brown, who works for the NSPCC, the leading UK charity for the prevention of cruelty to children, acknowledges the work that search engines already do, but says they could do more.

"What we think that the search engine companies could and should be doing more of is to be more proactive in flagging and providing what could be automatically produced warnings to people who are trying to make those searches," says Brown.

"So for example if someone's trying to make a search for clearly abusive and illegal imagery of children, an automatic warning could come up to say that they're searching for illegal material, that that's been noted and if they continue to do that, their information could be passed on to the authorities. And for some people, not all, who are interested in this material that could in itself act as a sufficient deterrent, we think."

International issue

But as far as the provenance of the images themselves are concerned this is a global issue. And the nature of it means that it cannot be solved by one government alone.

"A lot of these crimes are committed not in the UK, not even in Europe, but farther afield, and of course this imagery can be shared very easily," Brown says.

"So, what's absolutely crucial is deterrents and prevention, and thirdly, the identification and tracking of victims as well. Because for every image that's created and viewed, a child has been abused. And it's so important that those children, where at all possible, can be identified and located and then offered the help and treatment that they will need."

Iceland has taken the issue to another level. Earlier this year, the government drafted plans to restrict the distribution of all pornography - not just illegal images of child abuse as in Britain, but also adult porn. The fear is that even legal pornography could have a corrupting influence on children, who can easily access the sites online in a way that is very hard to control.

Helga Luthersdottir, a teaching fellow in Icelandic Studies at University College London, explained the thinking behind the proposed ban.

"What is going on is definitely an attempt to actually define pornography," she told DW. "And it's very much phrased within the framework of the good of the children. How do you protect children from actually seeing pornography that might damage their view of interaction between the sexes, for example? There's been a lot of discussion of how teenage boys have a warped or odd view of sexual relationships simply due to pornography."

If a ban on pornography happens anywhere in Europe, it's likely to be in Iceland.

However, defenders of the internet and of free speech were given a boost at the end of April when the government there was ousted by a new center-right coalition, which is less likely to pursue the proposals.

John Carr, the UK government advisor leading the calls for changes to search functions, is not in favor of going down the Icelandic route and banning all pornography.

"I've never, ever believed in censorship. If something is legal, it has a perfect right to be published - which means it has a perfect right to be on the internet," says Carr. "My position is different. I care what kids can get access to. I'm in the child protection business, not the adult protection business. If consenting adults want to do stuff with porn, that's their business."