Google will block more than 100,000 unique search terms that could lead to the discovery of child abuse images. The move follows UK government calls made earlier this year for search engines and Internet service providers (ISPs) to do more to prevent access to illegal material.
Microsoft is also preparing to announce its own efforts along with Google and other web firms and ISPs.
In a piece written for the Daily Mail, Google's executive chairman Eric Schmidt insisted his firm had listened to the government, and has added 200 people to its books dedicated to finding and removing images of child abuse.
Google, along with Microsoft's Bing search engine, had already been showing pop-up warnings and advice to users searching for illegal content. Schmidt said the warnings appear for 13,000 search queries on Google.
"While no algorithm is perfect – and Google cannot prevent paedophiles adding new images to the web – these changes have cleaned up the results for over 100,000 queries that might be related to the sexual abuse of kids," he wrote.
Further, Schmidt said Google would send engineers to the UK's Internet Watch Foundation and the U.S. National Center for Missing and Exploited Children, as well as funding internships for the organizations.
YouTube engineers have also been working on the problem, according to Schmidt, developing algorithms that can detect child abuse in videos. He said Google hoped to share the technology with other Internet video providers in the new year.
The move was welcomed by prime minister David Cameron, who made calls for such action back in July, calling it "significant progress". Cameron had given search providers and ISPs an October deadline to make changes.
"At the time, Google and Microsoft – who cover 95 percent of the market – said blocking search results couldn't be done, that it shouldn't be done," Cameron said. "I did not accept that then and I do not accept that now."
He warned that while Google and Microsoft's efforts were welcome, if they failed to act strongly enough, he would have to take legislative action.
"If the search engines are unable to deliver on their commitment to prevent child abuse material being returned from search terms used by paedophiles, I will bring forward legislation that will ensure it happens," he said.
Many believe, however, that the efforts so lauded by the government are merely rehashes of ongoing projects. In a column for ITV News, former CEO of the Child Exploitation and Online Protection Centre Jim Gamble said Cameron has "the best of intentions" but that he has been "poorly advised and ill informed".
"If you scratch the surface, it also evidences the fact that nearly everything was already in place," he said. "Some of these new tactics will help divert inadvertent access and perhaps delay a novice paedophile, but much of the hype in real terms will mean very little."
Despite the apparent increase in action from search providers, the problem of the so-called "dark web" remains, with ISPs the only gatekeepers between users and illegal abuse content. A task force led by Tech City boss and ex-Google and Facebook chief Joanna Shields will "explore what more can be done" to reduce its threat.
In addition to efforts from Google and Microsoft, the Internet Watch Foundation has been given a £1.5 million funding boost in order to hire more skilled analysts to seek out child abuse sites.
In his illegal content crackdown in July, Cameron called on ISPs to make their Internet-filtering tools stronger, and announced that some of the UK's biggest WiFi providers had signed up to a filtering agreement. However, the announcement was largely symbolic as all the providers involved were already undertaking content filtering.
Cameron's push for ISPs to put more robust filtering technology in place was criticized at the time, with industry bodies reminding the prime minister of the inherent flaws in such tools.