Google's new plan to link user data across its email, video, social-networking sites has come under fire from critics who say it's an invasion of privacy because of the sheer volume of information collected and the inability of users to opt out.

Under the plan, information collected about individuals will be integrated across 60 Google products including Gmail, YouTube and web search. Users will have to agree to a new privacy policy that will encompass data including location measurements collected on mobile devices.

The result is that Google will soon know more about who users are and what they do on the web, allowing it to target search results and advertising. Users will not be allowed to opt out of the changes, which take effect March 1.

In a company blog post, Google privacy director Alma Whitten says that "if you're signed in, we may combine information you've provided from one service with information from other services. In short, we'll treat you as a single user across all our products, which will mean a simpler, more intuitive Google experience."

Google also offered other ways that merging data will benefit users.

"We can provide reminders that you're going to be late for a meeting based on your location, your calendar and an understanding of what the traffic is like that day. Or ensure that our spelling suggestions, even for your friends' names, are accurate because you've typed them before," wrote Whitten. "People still have to do way too much heavy lifting, and we want to do a better job of helping them out."

However, the changes have provoked an outcry from critics who say Google is abusing its dominance in internet search to drive more traffic to its own services.

"Privacy advocates say Google's changes betray users who are not accustomed to having their information shared across different websites," wrote Cecilia Kang of the Washington Post. "A user of Gmail, for instance, may send messages about a private meeting with a colleague and may not want the location of that meeting to be thrown into Google's massive cauldron of data or used for Google's maps application."

Helps advertisers find customers

Google, Facebook and other popular internet services try to glean as much information as possible about their users so they can sell more advertising at higher rates to marketers looking to target people interested in specific products. Google says users who opt to see personalized ads are 37 per cent more likely to respond to an ad than people who opt out of targeting.

The company said the new system will give users more relevant search results and information, while helping advertisers find customers, especially on mobile devices. For example, if you spend an hour on Google searching the web for skateboards, the next time you log into YouTube, you might get recommendations for videos featuring Tony Hawk, along with ads for his merchandise and the nearest place to buy them.

"If you're signed into Google, we can do things like suggest search queries — or tailor your search results — based on the interests you've expressed in Google (Plus), Gmail and YouTube," the company said on a new overview page for its policies. "We'll better understand [what] you're searching for and get you those results faster."

The changes follow the demise of Google Buzz, which was shut down less than two years after being introduced. The social networking tool was ridiculed for exposing users' most-emailed contacts to other participants by default, inadvertently revealing some users' ongoing contact with ex-spouses and competitors.

Google has since made Plus the focal point of its challenge to Facebook's social network. In the first seven months since its debut, Plus has attracted more than 90 million users, according to Google. To promote Plus, Google recently began including recommendations about people and companies with Plus accounts in its search results.

Privacy audits

Google and the U.S. Federal Trade Commission reached a settlement last year that forbids Google from misrepresenting how it uses personal information and from sharing an individual's data without prior approval. Google also agreed to biennial privacy audits for the next two decades. Google said it talked to regulators about the upcoming privacy changes, which it will apply worldwide.

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Jeff Chester, executive director of the privacy group Center for Digital Democracy, said Google hopes "that by creating a one-stop shop for privacy policy it will deflect regulatory action."

With the move, Google said it has condensed 60 distinct privacy policies into a single one that is "a lot shorter and easier to read." Google is alerting users to the changes with a notice on its homepage that reads, "We’re changing our privacy policy and terms. Not the usual yada yada."

Ryan Calo, director for privacy at the Stanford Center for Internet and Society, said Google is trying to make its privacy policy transparent, but the company must ensure that the ways it uses data help users without revealing sensitive information.

"If it creeps people out, then they need to be aware of that," he said.   

Separate policies will continue to govern products including Google's Chrome Web browser and its Wallet service for electronic payments.

With files from the The Associated Press