Senator Charles Schumer said that billboard companies that track people's movements through smartphone apps in order to optimize advertising locations pose a threat to privacy.

He is calling for a federal investigation into Clear Channel Outdoor Americas' 'spying billboards,' warning the service may violate privacy rights by tracking people's cell phone data, reported the New York Post.

'A person's cellphone should not become a James Bond-like personal tracking device for a corporation to gather information about consumers without their consent,' Schumer said in a statement.

In a response, Clear Channel company spokesman Jason King said the RADAR program is based on an established advertising technique that 'uses only aggregated and anonymized information' from other companies that certify they're following consumer protection standards. It said that the characterization of its program is inaccurate, insisting it only uses anonymous data collected by other companies, reported the New York Post.

The company 'does not receive or collect personally identifiable information about consumers for use in Radar,' CEO Scott Wells wrote in a letter to Senator Al Franken, a Minnesota Democrat. 'It's not necessary for the insights we are offering our advertising customers.'

The ad program is a partnership between Clear Channel and technology companies, including AT&T, that gather location data from smartphone apps, the New York Post reported

Schumer said that an investigation into the company is necessary because most people don't realize their location data is being mined, even if they agreed to it at some point by accepting the terms of service of an app that later sells their location information.