A financial expert has issued Brits on holiday an urgent warning to avoid being hit with unnecessary fees. According to Martin Lewis, you could be charged as much as €7 a time just to withdraw cash.

Since the use of card and mobile payments has become easier than ever many of us no longer carry cash with us. However, there are still instances where cash might be needed - especially in other countries.

While it is relatively easy to access cash from ATMs during trips, you may not realise they come with some extra costs. On his website Money Saving Expert, Martin Lewis explained that some ATMs will charge sneaky withdrawal fees.

This isn't a fee for converting the cash but a charge for actually taking it out. And this can vary massively depending on which machine you use.

Martin said: "Beware overseas ATM charges. Don't think they're all the same, and watch for scare tactics.

"It's becoming more common for the actual cash machine to charge you when abroad. There's no way around this, but don't assume all ATMs charge the same."

Martin referenced his own experience in which he saw first-hand the extreme differences in ATM charges. "A couple of years ago, I did a cash machine experiment when I was filming abroad, and as part of it, often found ATMs within 200m of each other with withdrawal fees ranging from €2 to €7," he said.

"While the €7 fee machines did sometimes offer better exchange rates, that's irrelevant, as you should SAY NO to the foreign bank doing the conversion - you want your UK card to do it (especially if you've a specialist card)."

You should ignore any messages on the ATM screen to change your mind. Martin continued: "Foreign ATMs don't like that. They'll push and try to scare you to let them convert for you, with an 'are you sure?', or 'are you really sure?' if you select the option they don't want (as they make less money).

"Yet still say no to currency conversion. Do that and the only thing that matters is the fee, so go for the cheapest one of those."

Overall though he advised people to get any foreign cash you need before travelling. "In general, it's a safer bet to get cash beforehand, as you can research the very cheapest rates, but you're blind to what's out there, and especially in tourist resorts, you may find poor rates and limited competition," he added.

"I'm not saying overseas bureaux can't undercut UK ones, but they'd need be very cheap to beat the UK's cheapest, and it'd be rare to randomly stumble on that. The exception is if you know of a specific super-cheap bureau, for example, you go to the same place every year. Then absolutely, if you know what you're doing, wait."

You can use Money Saving Expert's travel cash comparison tool to see the best options for getting currency, here.