Joan Bolger isn't the first tourist to be ripped off in an ATM scam. So why is it hard to get help?

Be careful if you're off to the Canaries. You won't read about it in any brochure, but visitors to Gran Canaria are getting burned - and not by the African sun. Scores of tourists, including this one, have been left penniless and dejected by an ATM scam that is perhaps most remarkable for the lack of surprise it seems to arouse in banks and policemen. Oh, and don't expect the banks to refund what was stolen from your account with their machines: if it's anyone's fault, some of them imply, it's yours.

I was standing at an ATM in Playa del Inglés, trying to withdraw some hard-earned cash for another evening of holiday debauchery. I put in my Laser card and keyed in my PIN, but nothing happened. According to the woman next to me, it was one of the island's old machines, a dinosaur, and liked to swallow cards. I didn't want to give up, so I kept punching away: PINs, cancel buttons, return-card buttons, €100 buttons, €200 buttons. Nada.

The woman suggested coming back in the morning with my passport, to retrieve the card from the bank. It sounded sensible. But the next day the cashier said that the bank didn't have my Laser card and that it must have been stolen. We stood there like two children, squabbling over who was responsible. Me? The bank? The thief?

It was time to cancel my card. When I finally tracked down the emergency number for my bank at home, I discovered that €800 had been taken from my account: €400 the evening before and €400 that morning. It seemed I had been the victim of skimming, which police say is a common way to steal bank cards.

The thieves, they say, make a plastic sleeve, fractionally bigger than your card, and slip it into the slot of an ATM. When you put your card in, the machine knows it is there but cannot read it, so it flashes a message that your card is invalid. It might also ask you to retry your PIN.

And then the thieves get you. It might be with a hidden camera, with a sensor laid over the keypad or even with a discreet glance over your shoulder by a "helpful" stranger, but they record your PIN as you punch it in. Then, when you leave your card behind in frustration, they pull out the sleeve and retrieve it. Whether they use your card elsewhere or clone it, they have a direct route into your bank account.

When I got home to Cork, it turned out that everything about the transactions was traceable except my cash. My bank sent me the kind of impersonal letter you get when you're turned down for your first credit card. There was nothing it could do, it said. It was clear the thieves knew my PIN and equally clear I had given it away, unwittingly or not. How could it be liable? That my PIN was intercepted seemed not to mater. Some people are luckier, I've heard: some UK banks accept it's not the customers' fault and refund their money.

Two and a half weeks after my money was stolen, the bank summoned me to say that although the transactions were not refundable it would "assist in any further measures to take the case to the Ombudsman".

So until retina scanning replaces PINs, remember to treat everybody at an ATM as your enemy. And why not run your finger over the card slot, to feel for a plastic sleeve - there will be two bumps that thieves use to pull it out - or at least cover the keypad while you type your PIN? If all else fails, you can always console yourself with the fact that your tan will see you through weeks that your money wouldn't have.