A surge in demand has forced travel firm Thomas Cook to suspend its online currency sales to avoid running out of cash.
A vote for the UK to leave the European Union led to a sharp fall in the value of the pound, which had been rallying all week as markets bet the UK would vote to remain.
Thomas Cook has put a limit of £1000 on transactions at its high street branches.
The pound fell by 7.8 per cent against dollar to $1.3729 after the unexpected vote came in. A little earlier the pound was trading at €0.8066 against the euro – down 5.4 per cent today.
Sterling has racked up its worst daily fall on records that date back to 1971 — even uglier the collapse of Lehman Brothers, as well as Black Wednesday.
Read more: FTSE 250 suffers its sharpest ever drop
The sell-off also spread around equity markets, leading to a rush to safe haven assets.
Money changers across the country had queues out of the door yesterday as anxious holidaymakers rushed to change money ahead of the referendum.
In a statement Thomas Cook 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 fulfill outstanding orders. We hope to be back up and running as soon as possible.
Other money changers, such as the Post Office Travel Money and FairFX, have warned holidaymakers will be hit by currency swings in coming weeks if volatility continues.
There have been reports by Brits abroad, via Twitter, that some holiday destinations are refusing to change sterling due to lack of an exchange rate from central banks.
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