Complaints over online ads lead to new user control

Google founders and presidents Larry Page and Sergey Brin (EPA)

Internet users will be given the chance to escape tracking devices which follow their movements online as part of a clampdown on advertising, amid a marked decline in public trust in commercial messages.

A new symbol featuring the letter "I" inside a triangle will come into force in June on online adverts generated by "cookies", used by web companies to create personal profiles based on use of the Internet.

It comes as the Advertising Standards Authority highlighted a surge in complaints by more than 40 per cent. More than 20,000 campaigns provoked complaints in 2011 compared to 14,000 the previous year.

Data collected by cookies is used for Online Behavioural Advertising (OBA), allowing companies to direct adverts at individuals who, through the websites they have visited, have indicated an interest in certain goods or services.

The warning system, to be introduced by the European Advertising Standards Alliance and the Internet Advertising Bureau of Europe, allows users to opt out of OBA.

Guy Parker, chief executive of the Advertising Standards Authority, who today gives evidence to Lord Justice Leveson's inquiry into media standards, said: "Trust in advertising has been declining for a number of years and this is not good news."

His comments came as the ASA published two damning findings relating to commercial claims made by the world's largest travel website, TripAdvisor, and beauty brand L'Oréal.

The surge in the ASA's workload in the past year has been due partly to an extension of the watchdog's remit in March to include claims made on company websites. "Members of the public are complaining about claims they are seeing on company's own websites – it's pricing, issues to do with the availability of products and services and the performance of products," said Mr Parker.

The ASA is also investigating a Snickers campaign on Twitter in which celebrities posted pictures of themselves eating the chocolate bar.