Search engine Google has agreed to introduce measures backed by the British Prime Minister David Cameron to block child sex abuse content across its search engines.
The groundbreaking move will soon prevent illegal images and videos from appearing in more than 100,000 search terms associated with abuse.
Google says it has also developed technology that will allow illegal videos to be "tagged" so all duplicate copies can be removed across the internet. The changes will apply across the world in more than 150 languages.
Microsoft, which operates and powers Bing and Yahoo, will reportedly confirm at a Downing Street summit on online pornography in London today that it is introducing similar reforms.
Google chairman Eric Schmidt, writing in the Daily Mail ahead of the talks, said "We've listened. We've fine-tuned Google Search to prevent links to child sexual abuse material from appearing in our results".
Mr. Cameron welcomed the move as a "really significant step forward", but threatened to bring forward new legislation if search engine companies failed to deliver on their promises.
Calls for internet companies to take action against searching for illegal content grew following the trials of child killers Mark Bridger and Stuart Hazel earlier this year.
Bridger, who murdered 5-year-old April Jones, and Hazel, who killed 12-year-old Tia Sharp, both used the internet to search for child abuse images before the killings.
Senior figures from Google, Microsoft and BT were summoned to the UK Parliament for a meeting in June where they were told they had to do more to combat the issue.
UK & US are to create a joint taskforce to combat online child abuse
Mr. Cameron told the Daily Mail "We learnt from cases like the murder of Tia Sharp and April Jones that people will often start accessing extreme material via a simple search in one of the mainstream search engines".
The crackdown comes as Mr. Cameron is set to reveal at the summit that Britain's National Crime Agency is to join America's FBI to tackle online child abuse.
The transatlantic taskforce is being established by the US Assistant Attorney-General and the British to target criminals who use the internet to hide from the law.
It will be specifically tasked with tracking down offenders who use the "dark web" - secret and encrypted networks that are increasingly being exploited by paedophiles and other criminals.
The NCA estimates the number of UK daily users of secret or encrypted networks will have risen to 20,000 by the end of the year.
While some will be using them for legitimate purposes, UK law enforcement and intelligence agencies believe paedophiles involved in distributing child abuse material are using them to hide their identities.
At the same time a group of industry experts is being set up to look at new technical solutions for removing child abuse material from the the internet.
Joanna Shields is chief executive of Tech City UK and said it would be looking to spot the "threats of future" to protect the most vulnerable in society.
"It's vital that governments and industry work together to eradicate child abuse content from the internet, and that we mobilise the best and brightest in the technology industry to come up with innovative solutions to tackling this problem" she said.
John Carr is an adviser to the UN and secretary of the UK Children's Charities' Coalition on Internet Safety Child Safety. He welcomes the move.
