Lists can also be compiled by organisations – privacy rights groups, say, who may put together a comprehensive list of all third-party ad serving and tracking companies, which can then be downloaded and installed by web users.

Microsoft chief privacy strategist Peter Cullen said: “Some consumers today have been very clear that they have privacy concerns, like being unclear about what information is being shared and how it is used as they browse. Some sharing is good – you may want a shopping site to know your history – but it is hard for anyone to differentiate today.”

Earlier this month, the FTC came out in support of a system allowing people to use their web browser settings to opt out of having their online activity monitored for ad targeting purposes, though the Interactive Advertising Bureau cautioned such a system would be unworkable.

“The internet is comprised of millions of interconnected websites, networks and computers – a literal ecosystem, all built upon the flow of different types of data,” the bureau said. “You cannot turn off data sharing online and, if you could, consumers would encounter a severely diminished experience.”

Others objected to the idea of a ‘do not track’ system as inherently unfair to content providers who rely on ad revenue to fund their work.

Rik van der Kooi, Microsoft’s corporate vice president of advertiser and publisher solutions, wrote in a blog post that the advertising industry needed to adopt technologies that provide consumer choice and control over the sharing of personal data, while enabling more effective and relevant advertising and “highlighting the ‘value exchange’ that occurs when people receive the content they want that is ‘paid for’ by advertising”.

“We believe that the convergence of new privacy tools and robust advertising growth can, in fact, co-exist,” said van der Kooi.