Sen. Charles Schumer is calling on the Federal Trade Commission to investigate navigation-system company OnStar over policy changes he described as "one of the most brazen invasions of privacy in recent memory." 

The call comes after OnStar announced it would continue to track users after they discontinue service unless the customers explicitly opt out. Further, OnStar said it reserves the right to compile and sell information about drivers' habits to other organizations. 

While urging OnStar to reconsider, Schumer, D-N.Y., wrote to the FTC calling for a probe. OnStar is used by 6 million Americans. 

"I am concerned that OnStar may be abusing the consumer data -- including sensitive information like vehicle location and speed -- to which it has access," Schumer wrote. "These changes put consumers at risk for having sensitive personal data collected and shared without their knowledge." 

He asked the FTC to investigate whether the policy changes constitute "an unfair or deceptive trade practice." 

Regardless of the legal implications, Schumer said in a letter to OnStar executive Linda Marshall that the policies violate "the trust your customers put in you." 

"More troubling, it is a violation of which many may not be aware; a reasonable consumer would assume that when they terminate a service, they will no longer be monitored by the service provider," he wrote, urging OnStar to "dial back" the changes. 

But the General Motors Corp. OnStar service says customers are thoroughly informed of the new practice. If a customer says he or she doesn't want to have data collected after service is ended, OnStar disconnects the tracking. 

And although OnStar reserves the right to share or sell data on customers' speed, location, use of seat belts and other practices, a spokeswoman says it hasn't done so and doesn't plan to. 

"We apologize for creating any confusion about our terms and conditions," said Joanne Finnor, vice president of subscriber services. "We want to make sure we are as clear with our customers as possible, but it's apparent that we have failed to do this. ... We will continue to be open to their suggestions and concerns." 

Finnor noted keeping the two-communication active for former customers could someday allow for emergency messages to be sent even to ex-customers about severe weather or evacuations. 

The open line could also allow OnStar to alert drivers about warranty information or recalls, she said. 

OnStar charges about $199 a year for basic service and $299 a year for service that includes navigation aid. 

The Associated Press contributed to this report.