The weakness of the pound is not the only factor that will increase the cost of your holiday abroad this summer.

The number of banks that charge customers for using their debit cards overseas has almost doubled to 17 in the past year, according to research by uSwitch.com, the comparison website, with Nationwide and Thomas Cook introducing foreign transaction fees for the first time. The cost of using credit cards abroad has also risen, lifting lenders' earnings from these transactions by 6 per cent to £745 million a year.

If you take a debit card abroad you can now expect to be charged a conversion fee on every purchase, as well as a transaction charge. And it will cost you even more to withdraw money from a cash machine.

Those who bank with Lloyds TSB, for example, will find that for every £100 cash withdrawal, they will be stung for an extra £4.99 - a 2.99 per cent conversion charge and a minimum ATM fee of £2. Spending £100 in a shop on the same card will cost £3.99 - on top of the conversion charge there is a £1 retail transaction charge.

Using your credit card abroad is slightly cheaper, but you are likely to have to pay a foreign-usage charge of as much as 2.99 per cent each time a transaction is made. The worst culprits for imposing fees include HSBC, Alliance & Leicester and American Express. For every £100 you spend abroad on a credit card with any of these banks, you can expect to pay an additional £2.99.

Credit cards are even more expensive when you make cash withdrawals. On top of an average £3 ATM fee, interest is charged as soon as you withdraw the money - and at a much higher rate than usual.

So, what are the cheapest options for those who want to cut the cost of their holiday money?

Cash

Do not assume that a 0 per cent commission offer from a bureau de change means that holiday money is exchanged free of charge. In reality, uncompetitive exchange rates are equivalent to a commission charge of as much as 15 per cent.

The most expensive currency is sold to captive audiences, so avoid changing your money at airports and railway stations. At St Pancras International, the Eurostar terminal in London, you would have received only €189.26 for each £200 you exchanged last month, equivalent to a 13 per cent commission charge. This compares with €208.30 for Travelex in the same period. Remember, however, that if you take cold, hard cash on your travels, you have no security if it is lost or stolen.

Traveller's cheques

Trusty traveller's cheques remain a secure way of taking money on holiday and allow you to keep track of your spending, as you know before travelling exactly how much currency you receive for each pound. The exchange rates that you receive when you cash them in are not necessarily the most competitive, though, and you also have to find somewhere that will accept traveller's cheques.

Prepaid cards

If you want to combine the ease of plastic with the predictability of traveller's cheques, consider taking a prepaid currency card on holiday.

Similar to a pay-as-you go phone card, you can load a currency card with cash before you travel and use it as you would a credit or debit card. It is worth shopping around for the best deal, as some prepaid cards levy a small fee for transactions, though this is rarely as much as it costs to borrow money on credit.

As the market in prepaid currency cards is relatively new, you can load only euros or dollars on a card. The drawback is that if you are not holidaying in the US or the eurozone, you will be charged to change the money on your card into local currency.

The best-buy prepaid card is from CaxtonFX. You can apply free for its chip-and-PIN Global Traveller card and use it anywhere that accepts MasterCard. It costs nothing to make transactions or withdraw cash. You can top up the card online, over the phone or by text message before you go away and while you are abroad.

You can also apply for and top up FairFX's euro or dollar currency cards at no cost. Foreign transactions are free, but you will be charged €1.5, or $2, to use the card in overseas ATMs.

No-fee, or low-fee, credit and debit cards

If you stick to conventional cards, there are still a few good deals, but you will have the hassle of opening a new bank account or applying for a new credit card before you travel.

The Post Office is the only provider that does not charge for foreign transactions. Its Platinum credit card offers 0 per cent on purchases for three months. Nationwide will start charging 0.84 per cent foreign-usage fees on its credit and debit cards from May 6, rising to 1 per cent on July 1. But its Gold card will still be one of the cheapest to use abroad this summer.

Saga's Platinum credit card, meanwhile, has no charge for transactions within the EU and only 1 per cent for the rest of the world.

Coventry Building Society, the Co-operative Bank and Yorkshire Bank all have debit cards with no conversion fee, but they will charge for ATM cash withdrawals and purchases.