Microsoft's P3P privacy protection feature in Internet Explorer is impractical to comply with while providing modern web functionality such as cookie-based features, Google said yesterday in response to an accusation from Microsoft that Google had bypassed privacy protections in Internet Explorer.

Google is already facing allegations from Microsoft's corporate vice president for Internet Explorer Dean Hachamovitch that the company circumvented privacy settings in Apple's Safari browser to plant cookies on users.

"We've found that Google bypasses the P3P Privacy Protection feature in IE," he said. The result is similar to the recent reports of Google's circumvention of privacy protections in Safari, even though the actual bypass mechanism Google uses is different, he added.

But Google's senior vice president of communications and policy, Rachel Whetstone, countered that Microsoft's policy is "widely non-operational".

Newer cookie-based features are broken by the Microsoft implementation in IE, Google said. These include features such as Facebook "Like" buttons, the ability to sign-in to websites using a Google account, and hundreds more modern web services. It is well known that it is impractical to comply with Microsoft's request while providing this web functionality, Google added.

Google said it has been open about its approach on P3P, and so have other websites including Facebook.

The cookies Google uses to secure and authenticate an user's Google account, and store his preferences, may be served from a different domain than the website the user is visiting, Google said on its support site. "The P3P protocol was not designed with situations like these in mind. As a result, we've inserted a link into our cookies that directs users to a page where they can learn more about the privacy practices associated with these cookies," it added.

Whetstone also referenced a Facebook statement on its website, that the P3P standard is now out of date and does not reflect technologies that are currently in use on the web, so most websites currently do not have P3P policies. "The organisation that established P3P, the World Wide Web Consortium, suspended its work on this standard several years ago because most modern web browsers do not fully support P3P," it added.

Facebook was not immediately available for comment.