One in five will carry credit cards debts all year

We all know the drill with credit cards: you're supposed to borrow on them when you absolutely need to, but only for as long as you can without having to pay interest - whether that's just a month, or a longer interest-free period. Then we must pay them back in full.

Unfortunately, however, although we know the rules, new statistics reveal we find it impossible to stick to them - and in fact one in five of us are in pretty serious trouble.