Microsoft has introduced a "pop-up" warning on its Bing search engine that tells UK users that they are searching for illegal child abuse images.
The company said that anyone using the engine to search for such material will trigger the Bing Notification Platform message warning that tells them the content they are looking for is against the law and provides a link to a counselling service.
The move comes after David Cameron this week threatened to impose tough new laws on internet giants if they fail to blacklist key search terms for horrific images by October as part a crackdown on online porn.
A Microsoft spokesman said: "If someone in the UK tries to use search terms on Bing which can only indicate they are looking for illegal child abuse content, they will activate the Bing Notification Platform which will produce an on-screen notification telling them that child abuse content is illegal.
"The notification will also contain a link to Stopitnow.org who will be able to provide them with counselling.
"Due to the unique and sensitive nature of child abuse and child exploitation, Microsoft has been, and remains, a strong proponent of proactive action in reasonable and scalable ways by the technology industry in the fight against technology-facilitated child exploitation.
"The Bing Notification Platform is just one way in which Microsoft is working to tackle the scourge of online child abuse content.
"In addition, we have teams dedicated globally to abuse reporting on our services and the development of new innovations to combat child exploitation more broadly."
Microsoft said it already has a policy of removing links to illegal content as soon as possible.
The Bing Notification Platform is triggered by search terms on a list provided by the The Child Exploitation and Online Protection Centre (CEOP), Microsoft said.