There have been high profile cases where offenders had searched for child abuse images online
The prime minister has warned companies they need to act to block access to child abuse images on the internet or face legal controls.
David Cameron told the BBC’s Andrew Marr Show search firms like Google needed to do more to block “depraved and disgusting” search terms.
Google said when it discovers child abuse images it acts to remove them.
It is one of a number of firms which recently agreed on measures to step up the hunt for abusive images.
In June, the government said Google and others including Yahoo!, Microsoft, Twitter and Facebook would allow the Internet Watch Foundation to proactively search out abusive images, rather than just acting upon reports it receives.
But the prime minister said in the interview to be broadcast on Sunday that while internet providers and search companies were making some progress, he wanted search companies to block certain search terms from providing results.
“I think it’s wrong that they should get results and we need to have very, very strong conversations with those companies about saying ‘No, you shouldn’t provide results for some terms that are so depraved and disgusting.’
“I think there’s going to be a big argument there, and if we don’t get what we need we’ll have to look at legislation.”
He added that the extra steps he is demanding represented “an argument on behalf of Britain’s parents and children I’m prepared to have”.
A spokesman from Google responded, saying: “We have a zero tolerance attitude to child sexual abuse imagery. Whenever we discover it, we respond quickly to remove and report it.
“We recently donated $ 5m (£3.3m) to help combat this problem and are committed to continuing the dialogue with the government on these issues.”
Child protection experts say most illegal child abuse images are hidden and not available via search engines, the BBC’s technology correspondent Rory Cellan-Jones reported.
The debate about online images showing the sexual abuse of children has come to prominence following two high-profile court cases in which offenders were known to have sought child pornography online.
Mark Bridger, sentenced to life in May for the murder of five-year-old April Jones in Machynlleth, Powys, searched for child abuse and rape images.
And police who searched the Croydon home of Stuart Hazell, jailed for life in May for murdering 12-year-old Tia Sharp, said they had found “extensive” pornography featuring young girls.
During Sunday’s interview Mr Cameron also said he would like to see more restrictions on access to legal pornography that can be seen online by children.
He said that as a parent he worried “desperately” about it.
“There are rules about what films you can see in a cinema, what age you have to be to buy alcohol or cigarettes.
“But on the internet, there aren’t those rules, so we need to help parents with control,” he said.