is to start targeting its internet advertisements according to what people look at on the web, a controversial technique that privacy groups fear will give the search engine group even greater access to personal information.

The internet company will monitor the web pages that people visit and the YouTube videos they watch to create a profile of each user.

The company will then use the information to show display adverts to viewers based on those interests whenever they browse the web.

Google hopes advertisers will pay more for these targeted adverts, an important move at a time when the growth of online advertising is slowing down. A small group of advertisers will start using the system next month.