Internet giants could end up in the dock if there is another horrific case like April Jones Claire Perry, PM's adviser on childhood, said failure to remove vile images could lead to prosecution More than half of those who view child abuse images go on to commit abuse Mrs Perry said the companies were starting to look 'culpable' Victim: April Jones¿s killer was an online child porn addict Internet firms could be taken to court if child pornography is linked to more cases of sex abuse and murder. As David Cameron told Google and other web giants to do more to remove vile images, Claire Perry, his adviser on childhood, suggested failure to do so could lead to prosecution. "There's an interesting question if we have any more tragedies and internet activity is involved, whether there could ever be a case brought against one of these companies," she told the Mail. I don't think they want to get there, so they need to step up to their responsibilities. Research has suggested that more than half of those who view child abuse images go on to commit abuse themselves and concerns have also been raised over extremist material online in the wake of the Woolwich killing. Mrs Perry, Conservative MP for Devizes, said the companies were "starting to look culpable." That is a very uncomfortable position for them to be in. If you are a trusted brand trying to provide family entertainment - Sky, for example - you don't want to be in that position," she added. As well as suggesting the families of victims of criminals influenced by child porn might take court action, she said the Government could examine making the transmission of such material - as well as making or possessing it - an offence. Mr Cameron, Mrs Perry and Culture Secretary Maria Miller are to tell internet giants that "enough is enough" at a summit next week. Google, Microsoft, Facebook, Yahoo and other firms have been summoned to a Whitehall meeting where they will be told to consider urgent measures to limit access to harmful material. Ministers want warning screens to flash up telling people who attempt to access child porn sites which have been blocked that they risk breaking the law and losing their families and livelihoods. The Prime Minister said: "I am sickened by the proliferation of child pornography. That is why the Government I lead is convening a round table of the major internet companies, and demanding that more is done. There are encouraging signs that the industry is willing to step up, increasing funding and technical support for organisations combating child sexual abuse imagery online. The safety of our children is at stake. Mrs Perry claimed web firms themselves identified only around 5 per cent of illegal material which is then blocked. Mrs Perry (right) and Culture Secretary Maria Miller (left) are to tell internet companies that "enough is enough" "I find that astonishing," she said. Some 1.5million people see child abuse images by accident and only 40,000 report them. Child porn is illegal but the system only works when consumers stumbling across it report it. Imagine if that was the case in other areas - like the drugs trade for example. If the police suddenly said it was up to us to go out and find bags of heroin before they did anything about it. People wouldn't find that remotely acceptable. The companies have got to do more, whether it's providing filters or looking more actively at content. The five main internet service providers - BT, Everything Everywhere, Sky, TalkTalk, and Virgin Media - have made a commitment to offer filters to protect all devices in the home and will make selecting internet controls an "unavoidable step" for new customers. If customers choose not to engage - for example, if they just repeatedly click "yes" to get through set-up quickly - then that will lead to protections being switched on rather than off. Harriet Harman, Labour's shadow culture secretary and deputy leader, said: "The industry should be making safe search default, seeking robust age-verification systems and splash page warnings, and we should legislate if progress is not made." A Google spokesman said: "Google has a zero-tolerance policy on child sexual abuse content. Whenever we discover child abuse imagery we respond quickly to remove and report it to the appropriate law enforcement authorities.