WASHINGTON — A new Google tracking program that links shoppers' offline purchases to their web activity is drawing concerns over privacy and data security, and has prompted one privacy watchdog to file a federal complaint.

In the complaint, the Electronic Privacy Information Center (EPIC) formally requested the Federal Trade Commission to investigate the Store Sales Measurement program, which Google claims can prove online ads lead directly to in-store purchases.

The company used third-party partnerships to obtain access to the debit and credit card records of 70 percent of American consumers, the Washington Post reported.

The transaction data is encrypted and made anonymous using an algorithm that then matches it to users on Google and other Google-owned services.

The tech giant did not disclose the formula it uses to protect consumer data, but insists that the information remains safe and private, and that advertisers receive only aggregated information.

Google claims users can opt out easily by unchecking certain settings, but these settings are confusing and vague, according to EPIC.

Critics also worry that Google is putting consumers at risk, since even with encryption, the data could be hacked or breached.