The inventor of the World Wide Web has warned consumers to be wary of new technology being tested by three British internet suppliers which will track the websites users that visit to create personalised advertising.

Sir Tim Berners-Lee said he was concerned at the privacy implications presented by Phorm, a company that has invented a method of tailoring the adverts seen by internet users to their interests by monitoring the websites they browse.

The company is in talks with three of the UK's biggest internet providers – BT, Virgin and TalkTalk – about applying the system to their networks, provoking complaints that it can only function by using information that "belongs" to individual users.

Sir Tim, who is based in America but is in Britain to hold talks with government ministers, academics and corporations, said he did not want his internet service provider (ISP) to follow his "clickstream", or the websites he had visited, saying that such data could be put to negative use.

He told the BBC: "I want to know if I look up a whole lot of books about some form of cancer that that's not going to get to my insurance company and I'm going to find my insurance premium is going to up by 5 per cent because they've figured I'm looking at these books."

Sir Tim said the data used by Phorm belonged not to the ISP, which can sell it to advertisers, but to computer users such as himself. "It's mine – you can't have it. If you want to use it for something, then you have to negotiate with me." I have to agree, I have to understand what I'm getting in return."

Phorm, which has offices in London, New York and Moscow, insisted its technology did not permanently record a user's data and said it presented benefits such as warnings about so-called "phishing" sites, which try to con people into giving information such as bank details.

The phenomenon of linking an internet user's habits to the advertising they see is part of a growing trend on the Web. Several websites, including Facebook, have introduced systems which target advertising, leading to demands that customers be required to "opt in" rather than accept the practice as standard.

The Foundation for Information Policy Research, which campaigns on digital rights issues, said Phorm contravened legislation which protected consumers from the illegal interception of information. Phorm denied the claims, pointing out that the Home Office said the system was legal if users gave their consent.