0% introductory deals could have a sting in the tail

It found that about two-thirds of cards offering a 0% introductory rate will automatically move to a higher rate if a repayment is missed.

This means the cardholder will have to pay far more interest than would be the case under a 0% deal.

People were unaware of such "severe penalties", Moneysupermarket said.

Credit record

Missing a payment could also damage the credit record of the card holder.

A damaged credit record can mean that it is harder and more expensive in future to obtain credit.

Rob Kenley, head of credit cards at Moneysupermarket.com, advises cardholders to set up a direct debit to ensure that they do not miss a monthly repayment and incur extra interest costs.

"To avoid missing any payment it is vital people set up a direct debit to repay the minimum sum required each month against their balance," he said.

"They should also make additional payments whenever possible."

Rate tarts

Low and 0% interest-rate offers have grown in popularity over the past few years reflecting the ferocious competition among card companies determined to lure new customers.

This has led to the phenomena of the "rate tart" - people who move their debts between credit cards to take advantage of low-interest introductory offers.

The deals usually offer an interest rate of 0% for up to a year, and cost the industry an estimated �1bn a year.

However, credit card companies have been increasingly looking at ways of reducing the cost of offering these deals.

The most common route lenders have chosen is to charge a handling fee - typically of about 2.5% of the balance being moved - for transferring debt onto a 0% card.