Sen. Charles Schumer says major retailers are tracking shoppers through their smartphones without their knowledge.
Schumer says sophisticated monitoring software allows stores to track a customer's movements while in their stores and then save the data.
He says stores like American Apparel, Family Dollar, Swatch and Benetton are all either using or testing the technology.
Schumer says the stores are tracking signals put out by customers' smartphones to gather information like what part of the store shoppers spent time in and what products they have considered.
He is asking the Federal Trade Commission to require retailers to give shoppers a clear and obvious opportunity to opt out before they are tracked.
Currently, if a shopper does not want to be tracked, he or she must turn off the phone's WiFi, or leave it at home.