British Prime Minister David Cameron will demand internet search engines take action to block child sex abuse images.
"There are some searches which are so abhorrent and where they can be no doubt whatsoever about the sick and malevolent intent of the searcher that there should be no search results returned at all," Cameron will say in a speech in London on Monday.
"So I have a very clear message for Google, Bing, Yahoo and the rest. You have a duty to act on this -- and it is a moral duty."
According to extracts issued by his office, Cameron will give the companies until October to comply, saying all the "great brains" who work for them should be able to overcome any technical difficulties.
"I can tell you we are already looking at the legislative options we have to force action," he will say.
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Cameron has been pressuring internet companies to tackle online abuse for several months, after two high-profile trials over child sex murders in which the killers were both found to have searched for child porn online.
"This is quite simply about obliterating this disgusting material from the net -- and we will do whatever it takes," he will say.
Companies like Google say they already remove any abusive images of children as soon as they are reported, and the US internet giant insists it has a "zero tolerance attitude" to such content.
Jim Killock, head of the Open Rights Group which defends internet freedoms, says he does not believe the prime minister's proposed 'blacklist' of search terms will have any real impact.
Most child abuse images are circulated in private networks or sold by criminal gangs, he says.
In a blog posting, he concluded that the proposed policy "is likely to be of highly marginal impact".
Australian internet search providers are required to block any websites listed on Interpol, but cyber safety expert Susan Mclean says the Australian approach is disjointed.
"We can have codes of conduct and we can have gentlemen's agreements, but when they're not working or when they're not keeping pace with the volume of content we're seeing, there does come a time where governments needs to mandate it," she says.
