Anita Hare thought she was playing it smart when she took advantage of a low introductory interest rate on her Chase credit card to buy a Harley-Davidson motorcycle last spring. For four months, the 46-year-old from Baltimore County said, she paid her bill on time at a rate of 3.99 percent. Then she missed one payment by a few days — and her rate shot up to 28 percent, she said. The higher rate has pushed her balance above the original cost of the Harley.

"I was so careful not to let that happen," she said. "I've been absolutely livid."

Situations like Hare's are the target of sweeping new regulations approved by the Federal Reserve late last year that promise to change the way the credit card industry does business. But the rules do not take effect until 2010, and advocacy groups say consumers are still struggling with mounting debt and tightened access as the credit crisis helps fuel the economic downturn.

"It's the worst of all possible worlds," said Travis Plunkett, legislative director of the Consumer Federation of America.

"We know that these practices are not justifiable, and yet federal regulators have given the credit card industry a year and a half to continue to use them."

The average standard rate on credit cards declined from 15.21 percent in February 2007 to 14.03 percent last month, according to IndexCreditCards.com, as the Federal Reserve slashed a key interest rate to close to zero. Interest rates are expected to fall further as a $1 trillion government program to spur consumer lending gets underway.

But those averages do not reflect penalty rates that lenders may charge for late or missed payments. According to a survey last year by Consumer Action, an advocacy group, those rates average 26.87 percent.

Since the beginning of this year, said Bill Hardekopf, chief executive of LowCards.com, an independent review site, several companies have raised rates, increased fees and adjusted rewards programs.

"They have been very much damaged by this economic downturn and tightening of credit and all the losses that their banks have faced," he said. "If you as a consumer do anything to increase your risk, you will probably very quickly be hit."

Congress is considering legislation that would essentially force lenders to adopt measures similar to the Fed's within as little as 90 days. But the credit card industry and federal officials say the scope of the new rules make such a quick turnaround virtually impossible.

The regulations issued by the Federal Reserve, the Office of Thrift Supervision and the National Credit Union Administration in December ban "unfair and deceptive practices." The rules prevent banks from raising interest rates on existing balances unless a payment is more than 30 days late, charging late fees without giving a borrower a reasonable amount of time to pay and applying payments so that debts with higher interest rates are repaid last.

Federal officials and industry groups said moving too quickly could cast doubt on the accuracy of those calculations, scaring off investors who buy the debt and help fund new lending.

"It is our belief that this impact will be broad and not uniformly positive, potentially leading to reduced access to credit for millions of Americans and small businesses at the very time when they need that access to credit," said Kenneth Clayton, general counsel of the American Bankers Association, a trade group, in written congressional testimony.