Is OnStar turning your car against you? Senator Schumer thinks so.

OnStar, the in-vehicle emergency service, is the latest technology coming under fire from privacy advocates who say it is unfairly conducing surveillance on its users without their permission.

Several US senators, led by Charles Schumer (D) of New York, are asking the company to abandon the practice, which he and others say is becoming pervasive. Senator Schumer is also asking the Federal Trade Commission to investigate OnStar following the company’s announcement last week that it will continue to track the movement and speed of users even after they cancel the service, which is available by subscription.

Apple, Facebook, and Google have also come under fire this year over concerns about unwanted surveillance. The problems are the product of technological advancements that have outpaced privacy regulations, say analysts, with OnStar offering further evidence of how companies can collect data about their customers.

OnStar is owned by General Motors and, according to the company, is available in 40 2011 model vehicles. More than 6 million people have the service, the company says.

In a letter sent to OnStar's president, Linda Marshall, Schumer called the policy a “brazen invasion,” particularly because the company acknowledges it will maintain a connection with the user’s vehicle even after the user opts out of the service.

OnStar’s two-way location technology is marketed for its safety benefits: helping locate roadside services, provide alternate driving instructions, and sending help in case of an emergency. A spokesperson for the service did not respond by deadline to requests via e-mail and phone for comment.

Other companies have been criticized for not telling users if and how they collect personal data. For those that do, the warnings are sometimes in small print, critics say.

In April, for example, independent researchers said Apple and Google store the location history of iPhone and Android users, respectively. Both companies denied the charge.

Privacy advocates say the challenge is that embedding mobile software that protects user data is more costly. Companies failed to prioritize these kinds of protections when web browsers, smart phones, and digital tablets were being designed. That means mitigating the problem after the fact would involve changes far beyond amending user agreements. It would require redesigning the core structure of the technology.

“All these amazing new technologies ... were not designed to go the extra mile and work in a privacy friendly way. In fact, it’s often much more convenient to collect more information about where the device is and where it is going than to collect less,” says Peter Eckersley, technology projects director for the Electronic Frontier Foundation in San Francisco.

Much of the problem has to do with global-positioning software (GPS) that companies use to create a two-way communication with consumers. On one hand, it helps provide street directions or tell users where they are at any given moment. On the other hand, personal data on shopping habits or browser search history can also be stored without the user’s knowledge.

Companies like Facebook argue that tracking these data helps the company tailor the user’s online experience, directing the user to content of interest. But privacy advocates like Mr. Eckersley say companies are really interested in building data banks they can sell or use as leverage in partnerships with outside media partners.

“There’s no question that industry views this giant network of surveillance devices as a great commercial opportunity,” he says. The danger, he says, is that the information may “accidentally” be accessed by people – including the government, Internet stalkers, or hackers – who can have more nefarious intentions.

Regulation remains far on the horizon. There is no federal law that explicitly inhibits companies from using location tracking of its users.

One reason is the speed at which technology is moving, says Chenxi Wang, an analyst with Forrester Research in Foster City, Calif. “The privacy laws and regulations have not caught up with the technology,” she says.

But the spread of smartphones and tablets could create pressure for reform. Forrester Research forecasts that one in every three adults in the US will own a tablet by 2015. “Consumers are more aware of the [privacy] issue now, but whether they are turned off by the location tracking still remains to be seen,” says Ms. Wang.

For now, consumers concerned about privacy have to opt out of the digital realm or invest in software that blocks data storage. Neither, however, is likely to be a adequate solution, says Eckersley, who says a more realistic answer will come only from within the industry itself.

“We need to put pressure on what we want to see regarding privacy regulation. That is going to create better incentives for the industry to do the extra engineering legwork that is required to give us these cool new features based on what we’re doing in a way that doesn’t keep a record of where we were and what we do and what we read,” he says.