WASHINGTON (Reuters) -The top U.S. agency for consumer financial protection will scrutinize credit card reward programs after a surge in customer complaints, its chief said on Tuesday.

Rohit Chopra, director of the U.S. Consumer Financial Protection Bureau, has clashed with credit card issuers since last year over regulations capping late fees.

"We are going to be looking into the credit card rewards market due to an increase in consumer complaints," Chopra told reporters on the sidelines of an industry conference in Washington.

His remarks signaled the agency could also issue rules or take enforcement actions against banks offering products aimed at affluent clients.

"What the marketing gurus and consultants are telling credit card issuers is that they should focus consumers' attention on splashy rewards, but then withhold information from them when they're paying lots of interest and could switch to a lower-rate card, even within the same bank," Chopra said.

Credit card issuers sometimes hide the "darker side" of their offerings of cash back, miles and points in their terms and conditions, Chopra told attendees at the Consumer Bankers Association conference earlier Tuesday. The fine print allows card issuers to revoke rewards or make points difficult to redeem, he said.