Women's groups are calling on the Prime Minister to close a legal loophole that gives animals and dead people better legal protection than women and girls when it comes to internet pornography.
In a letter in Tuesday's Daily Telegraph, they warn that depictions of rape scenes are legal as long as the actors involved are over the age of 18.
Yet the same law makes possessing images of bestiality or necrophilia illegal, meaning animals and corpses have more rights than women and girls.
Their letter comes as internet and technology giants, including Google and Microsoft, are to meet culture secretary Maria Miller in Westminster where they will come under "unrelenting" pressure to do more to tackle online child porn.
Miller will tell the organisations to produce plans to combat the spread of child abuse images by the autumn.
Internet firms have already taken some action under pressure from ministers and in the wake of recent high-profile cases of child murder, but Mrs Miller will urge them to go further.
Mark Bridger, who killed April Jones, and Stuart Hazell, murderer of Tia Sharp, were both found to have accessed child and violent pornography and some experts argue there is a clear link between their obsessions and their actions.
BT has announced that any of its customers attempting to access web pages on the Internet Watch Foundation (IWF) list of identified images of child sexual abuse will now see a message telling them that the site is blocked and the reason why.
Under the current system, the site is blocked, but internet users only see an "Error 404" message.
Google has donated £1 million to the IWF, which is responsible for policing criminal content online.
But Mrs Miller said the firms could do more if they "seriously turn their minds" to the issue.
Representatives from Yahoo!, Google, Microsoft, Twitter, Facebook, BT, Sky, Virgin Media, TalkTalk, Vodafone, O2, EE and Three are due to attend the summit.
The letter calling on David Cameron to close a legal loophole and "take urgent action against violent and misogynistic pornography online" has been signed by Mumsnet, the National Federation of Women's Institutes, the Trades Union Congress, rape crisis centres and academics at Durham University.
"We specifically want the Government to close a loophole in the pornography legislation that allows the lawful possession in England and Wales of pornographic images that depict rape, so long as the actors are over 18," the letter says.
"This means that images titled 'teen slut rape' and 'schoolgirl rape' are lawful to possess. Depictions of necrophilia and bestiality are criminalised by the same legislation, meaning that animals and dead people are better protected than women and girls.
"A change in the English law would send a clear message that it is illegal to possess pornographic images that promote sexual violence against women.
"We are dismayed that this loophole exists, especially at a time when the media carries many stories about the sexual abuse of women and girls, including the recent convictions for murdering young girls of Mark Bridger and Stuart Hazell, both cases involving violent pornography."
The Children's Commissioner has also found that children have easy access to online pornography, which influences boys' harmful attitudes and behaviour towards women and girls, the group noted.
"We are concerned that 'rape porn' undermines the Government's efforts to tackle sexual violence," the letter says. "The government should close this loophole immediately."