David Cameron has pledged to use the intelligence services to investigate the "dark net" where paedophiles share materials on peer-to-peer online networks after child protection agencies warned that new security measures announced by Google and Microsoft would do little to tackle such crime.

Read more:

Download the new Independent Premium app Sharing the full story, not just the headlines

Ian Burrell: The 'massive breakthrough' where little has changed

The Prime Minister claimed a "massive breakthrough in cleaning up the internet" after the two Internet giants, which have been under pressure from Downing Street to do more to combat child abuse images, announced steps to block child sexual abuse material from appearing in results for 100,000 specific search terms. Google and Microsoft will use "photo DNA" to track pictures and videos of child sexual abuse and automatically remove them from the web. Mr Cameron said the changes marked "real progress against the absolute evil of child abuse".

But experts in the field said yesterday that the changes - also hailed by the Daily Mail as a "stunning victory" for its long running campaign against internet porn - would have minimal effect because paedophile networks avoided using the big search engines. Jim Gamble, former chief executive of the Child Exploitation and Online Protection Centre (CEOP), told the BBC: "I don't think this will make any difference with regard to protecting children from paedophiles. They don't go on to Google to search for images. They go on to the dark corners of the Internet on peer-to-peer websites."

Martyn Thomas, who chairs the Institution of Engineering and Technology (IET) IT Policy Panel, agreed. "There are better and more effective ways to protect children," he said. "The measures will help to protect young children from accessing such material, but they will do little for the people sharing these images which is being done through private peer-to-peer networks."

Google, in particular, has been under intense media and political pressure for months to take more action over fighting child abuse images and Eric Schmidt, the company's executive chairman, yesterday wrote an article for the Daily Mail in which he said "we've listened". Google has deployed a team of more than 200 to investigate using "state-of-the-art technology" to tackle the issue, he said.

Although Mr Schmidt claimed Google and Microsoft "have been working with law enforcement for years to stop paedophiles sharing illegal pictures on the web", the Mail described the new initiative as "a stunning U-turn by Google".

Google and Microsoft, which operates the Bing search engine, will post warnings in response to 13,000 explicit search terms, telling people the consequences of their actions and advertising child safety agencies. The search initiatives are global and will apply in 159 languages.

Later, following claims by experts that the real problem was with the private networks, Mr Cameron told BBC Radio 2 that he was prepared to call in the intelligence services. "There has been a lot in the news recently about the techniques, ability, and brilliance of the people involved in the intelligence community and GCHQ and the NSA in America. That expertise is going to be brought to bear to go after these revolting people sharing these images on the dark net and making them available more widely."

Mr Cameron was speaking after an Internet Safety Summit at Downing Street, attended by Internet Service Providers, the National Crime Agency (NCA) and child protection organisations. The Prime Minister said the NCA would provide a "step-change in our enforcement action to bring paedophiles to justice".

The UK government will host a further international summit on Internet safety next year. Mr Schmidt said he "welcomed the lead taken by the British government", while Microsoft chief executive Steve Ballmer spoke of allying with Downing Street and British child protection groups in "stamping out these horrific images".

Daily coronavirus briefing No hype, just the advice and analysis you need Enter your email address Continue Continue Please enter an email address Email address is invalid Fill out this field Email address is invalid Email already exists. Log in to update your newsletter preferences Register with your social account or click here to log in I would like to receive morning headlines Monday - Friday plus breaking news alerts by email Update newsletter preferences

Read more: