Lawmakers are asking federal regulators to conduct an investigation on Verizon Wireless for deploying supercookies to track online activities of subscribers.

Verizon Wireless uses alphanumerical codes known as supercookies to track and segment customers into groups. The wireless carrier then customizes adverts to pitch to these specific groups of subscribers accordingly by monitoring their web habits on the cellphone.

While the biggest network operator in the U.S. gives subscribers some options pertaining to the usage of their personal details for marketing, Verizon does not give customers the option of removing themselves from being tagged by the unique tracking codes.

On Friday, Feb. 6, senators sent letters to the FTC and FCC notifying the regulatory bodies that Verizon's tracking technology potentially violates the privacy of consumers. The letter also asked the regulators to look into the matter and examine Verizon's practices.

"This whole supercookie business raises the specter of corporations being able to peek into the habits of Americans without their knowledge or consent," said U.S. Sen. Bill Nelson. "That's why I think we need to get to the bottom of this and perhaps new legislation."

The lawmakers issued the letters on the heels of a report by Jonathan Mayer who exposed that the marketing software company Turn was misusing the supercookies to track customers for marketing drives. The marketing firm's nefarious activities pertaining to the "zombie cookies" were reported by ProPublica in mid-January.

"The company, called Turn, is taking advantage of a hidden undeletable number that Verizon uses to monitor customers' habits on their smartphones and tablets. Turn uses the Verizon number to respawn tracking cookies that users have deleted," reported the publication.

Turn revealed at the time that it will terminate the usage of the Verizon supercookies until the time the company's practice was re-evaluated.

Nelson and lawmakers Edward Markey, Richard Blumenthal and Brian Schatz have questioned Verizon if the company intends to continue using the supercookies, as well as the steps it will take to safeguard the privacy of consumers.

Verizon has revealed that the company has a fix in the works, which will enable subscribers to opt out of such marketing. Nelson, on the other hand, wants Verizon to give consumers the opt-in option.