The UK's deadliest plastic

Don't let tasty benefits and offers tempt you into applying for these credit cards.

I'd like to ask you to carry out a little experiment for me. Take out your wallet, open it up, and look at your credit cards. Now I'd like you to have a think about why you chose those particular cards. Most importantly, do you know how much interest you're being charged on each when you use it?

Most people don't. If you're one of them, you are probably paying far more interest than you need to.

Most expensive credit cards

If you religiously pay off your credit card balance in full each month, then you don't need to worry about how much interest you're charged - because you never have to pay any.

But if you're in debt on your card, then you should make sure you know your card's Annual Percentage Rate (APR). APRs can vary considerably from card to card, and the higher they are, the more interest you pay.

The problem is that certain credit card providers will offer you exciting benefits to try and disguise the fact that the APR on their cards are astronomically high. Just take a look at these:

NB: the APRs take account of both interest charged and annual fees.

Looking at this chart, you'll probably have noticed a common theme -- either these credit cards are targeting those with a less-than-perfect credit history or they're trying to dazzle you with 'fabulous' travel deals to encourage you to sign up.

If you're a regular traveller, you may find that signing up to one of these premium cards works to your advantage. But you'll need to use the bonus deals a lot to justify the fee. If you do decide to use one of these cards, please ensure you can afford to pay off the bill in full each month -- otherwise you'll be hit with an unbelievably high rate of interest. And that could far outweigh the benefits.

How high APRs affect you

Although anyone who owns a credit card should be paying off the bill in full each month, in some cases, that's just not an option. So instead, many of us opt to pay the minimum monthly repayment (MMR).

But the problem with this is that lenders often set the MMR at astonishingly low levels and that means it can take a very long time for you to clear the balance. What's more, you'll be paying out a lot in interest.

APRs don't have to be as high as the ones mentioned above for this to become a problem. For example, say you borrow £2,500 on a credit card which charges an interest rate of 19.9% and has a MMR of 2.5%. By only paying the minimum monthly repayment, it will take you a whopping 29 years and two months to pay it off in full. And over this period you'll have paid a mammoth £4,343.56 in interest. Now that's a scary thought.

And if that's the damage caused by using a credit card with an APR of 19.9%, imagine how bad it would be if you had an APR of 51.8% or 46%. In fact, using this nifty credit card calculator you'll see that you won't even be able to repay your debt. Now that really is scary.

The alternatives

I think credit cards with high APRs should be avoided at all costs -- no matter how tempting the rewards or benefits of the credit card might be. Even if you think you'll pay off the credit card balance in full each month, there may come a time when you simply can't and it's just not worth that risk.

The only time you should consider using one of the cards mentioned above is in exceptional circumstances, such as strengthening your credit record. You can read more on this here.

Whatever you do, don't ignore the interest rate on your credit card any longer! Switch to a better rate today!

More: A deck of different credit cards | Three credit cards I like | A handy alternative to credit cards