The web giant can link users' YouTube viewing, Google Maps searches and web history with their Gmail accounts -- leaving the company privy to personal information about individuals, which it will then use to attract advertisers.
Digital rights group Electronic Frontier Foundation (EFF) said, "This protection was especially important because search data can reveal particularly sensitive information about you, including facts about your location, interests, age, sexual orientation, religion, health concerns, and more."
The San-Francisco based organization advised Google users to delete their web history, which is done by clicking into the search engine's Web History page, selecting "remove all Web History" and confirming the opt-out.
Even users who remove their web history will have their data collected and stored by Google for internal purposes. The information will be connected to users' browsers, rather than their accounts, and will be partially anonymized after 18 months.
Google implemented the privacy changes despite European regulators warning Tuesday that the new policy could be illegal.
In a letter to Google Chief Executive Larry Page, French regulator CNIL said it had "strong doubts" about the legality of the changes and its compliance with European data protection legislation.
A British civil liberties group warned Thursday that nine out of 10 users have not read the new rules.
Big Brother Watch's Emma Carr told Sky News, "People don't realize just how big this is. All their information will be amalgamated in one profile. My personal fear is that if you are searching for health symptoms you might get an ad for a wonder drug. This is putting advertisers' needs first."