Travel firm Thomas Cook has suspended its online currency sales after unprecedented demand overnight.

The fall in the value of sterling, after a sharp rise earlier in the week, had tourists rushing to exchange money.

The euro was in particular demand, with the pound down more than 5% against the currency at €1.2398 in Friday trading.

At the travel money operation at the Post Office, Andrew Brown said holidaymakers should "watch currency movements very carefully".

The pound plunged to its lowest level since 1985 following the EU referendum. Sterling was down against every single major currency group, falling 10% against the dollar overnight to $1.33, a low not seen in 30 years.

Shares and pound plunge on Leave vote

How will Brexit affect your finances?

Throughout the night the Thomas Cook had been offering euros for click-and-collect at Thursday's favourable rate of €1.27 to the pound, despite the fall in the value of sterling in the wholesale foreign exchange market.

A rush of demand from holidaymakers trying to protect themselves against the fall led to queues snaking outside the doors at some Thomas Cook outlets this morning.

The company suspended the online service to make sure that its counters did not run out of cash.

Image copyright AFP

A Thomas Cook spokesperson said: "We have temporarily suspended our travel money website following unprecedented customer demand for foreign currency overnight and this morning.

"We apologise to all customers affected. Our immediate priority is to ensure that we have enough currency in store to fulfil outstanding orders. We hope to be back up and running as soon as possible."

'Do your homework'

Ian Strafford-Taylor, chief executive of currency provider FairFX, said the reaction of the pound to Brexit could signal "longer term volatility", with holidaymakers "directly impacted".

He said: "Those consumers who did not stock up on their holiday money may find their holiday now becomes more expensive this year, if weak pound-euro rates continue into the summer."

Andrew Brown, of Post Office Travel Money, which accounts for around a quarter of all UK foreign exchange transactions, urged holidaymakers to "watch currency movements very carefully".

He said: "For those who have not yet booked their holiday but are planning to travel abroad during the summer or later in the year, it will be well worth doing some homework before making a decision.

"Choosing a destination where sterling is strong and also where the local cost of living is low could make a significant difference to how far the holiday budget will stretch."

Joel Brandon-Bravo, UK managing director of travel deals company Travelzoo, warned the referendum result would affect the tourism industry in several ways.

He said: "The next 24 months of negotiations will be crucial for British travel - particularly if the UK Government wants to maintain inbound tourism from the EU, and avoid a price hike for Britons wanting to travel abroad for holidays."