Google has created a storm of protest by launching a controversial service that modifies web pages and directs users to sites chosen by the search engine.

AutoLink, which is included on Google’s popular desktop Toolbar, automatically inserts links in web pages. For instance, an address could be linked to a map supplied by Google or a book’s ISBN number to the page on Amazon.com, where the product is available to buy.

The Google service has raised the ire of several bloggers who have argued that it sets a worrying precedent, with publishers losing control of their work and users losing control of their desktops.

The Exchange Security website said: "Google's widely publicised mantra of 'don't be evil' is increasingly often being used to excuse behavior for which Microsoft, Oracle, or IBM would be roundly condemned."

Others have countered that users are free to opt in and out of products such as AutoLink and that critics risk stunting exciting new ideas.

"You can't argue that they are changing the website in any way and therefore messing with the author's right to link or not to link," Michael Gartenberg, the Jupiter analyst, said of Google in his blog.

A Google spokesman told Times Online: "AutoLink adds useful links to a page but does not replace any existing links. This version of the Google Toolbar is in beta, and we're looking for feedback from users to determine if these features are useful."

Google’s AutoLink recalls an earlier Microsoft invention called Smart Tags which the software company had planned to build into Internet Explorer, its market-leading internet browser.

Microsoft retreated from the idea despite winning a key patent case after opponents of the technology pointed out that Smart Tags gave the company the ability to determine which content providers — including itself via MSN — were used to satisfy queries. The New York Times was among those who spoke out against the product in an editorial.

Bloggers have been quick to draw comparisons between Google and Microsoft, which are fierce rivals. Microsoft recently launched its own search engine, going head-to-head with Google in the lucrative paid-search advertising market

"Google is to the Web what Microsoft is to PCs - the operating system everyone uses to search ... And millions use the Google Toolbar. They shouldn't get away with what Microsoft was unable to," the blogger Steve Rubel wrote on his Micropersuasion blog.

Other commentators have asked whether Google risks infringing copyrights by modifying pages without their author's consent.

It has also been reported that Barnes & Noble, the American bookseller, has been in talks with Google. It is likely that executives discussed AutoLink, which only sends users to Amazon.com.

Commentators have also queried whether it is healthy for companies that enjoy dominant market positions to alter pages without their author’s consent before they have been seen by readers.

"It opens up the floodgates for other ToolBar developers, and for MSN to re-introduce Smart Tags," said one contributor to an online forum on www.webmasterworld.com.

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