The Federal Reserve and two other banking regulators are set to unveil Friday one of the most aggressive efforts in decades to crack down on the credit card industry, prohibiting practices such as arbitrarily raising interest rates on outstanding balances.

The proposed regulations, which could be finalized by year's end, would label as "unfair or deceptive" practices that consumers have long complained about. That includes charging interest on debt that has been repaid and assessing late fees when consumers are not given a reasonable amount of time to make a payment. When different interest rates apply to different balances on one card, companies would be prohibited from applying a payment first to the balance with the lowest rate.

"It's stronger than what has been issued in the past," said William Ruberry, a spokesman for the Office of Thrift Supervision, which has joined the Fed and the National Credit Union Administration in backing the proposals. "What they proposed is a significant set of rules governing credit card practices and overdraft protection."

In the past, the agencies have regulated the industry by forcing card issuers to better disclose terms and conditions to customers. Last summer, the Fed proposed requiring card companies to improve their disclosures, a plan still being considered. But this new proposal, a summary of which was released by the OTS and the NCUA Thursday, would send a clearer pro-consumer message, said credit card watchdogs and government officials.