According to MORE TH>N most credit card customers are unaware of the interest rate on their card.
Research from the firm shows 15.7 million people (55 per cent of cardholders) do not know what rate they are paying.
Graham Hollebon, head of MORE TH>N credit cards said: "It's concerning that significant numbers of people, especially those with multiple cards, do not know what interest rate they are paying."
Additionally 64 per cent of the people surveyed by MORE TH>N have held onto the same credit card for three or more years.
Perhaps more worryingly, as many as ten per cent of people who took out a card out in the 12 months say they did not look at what interest rate they would be paying first.
"With nearly half of people using their credit card for everyday purchases, but a significant number still not paying their balance back in full each month, it is crucial that cardholders are fully aware of the consequences of their actions," said Mr Hollebon.
"There are a vast array of deals available on the market and there's absolutely no need for people to stick with uncompetitive cards," he added.
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