Holidaymakers travelling to Europe this summer are being urged to buy their euros as soon as possible.
The pound is expected to spiral after the predicted election of Boris Johnson.
Either Mr Johnson or Jeremy Hunt will become the new Conservative leader as the result of the ballot will be revealed just before midday.
The succeeder, presumed to be Mr Johnson, will officially become prime minister on Wednesday.
While this might be a point of enthusiasm for those pushing for a low-tax economy and a hard Brexit , people looking to build up some foreign reserves may be less enthusiastic, the Mirror reports.
It is expected the value of the pound will plummet if and when Mr Johnson is announced as the winner of the leadership campaign.
The currency's falling value in relation to the euro and US dollar means those planning a trip abroad will be out of pocket.
Currency traders are thought to be unimpressed with Mr Johnson's 'do or die' attitude to Brexit, with foreign investors likely to think twice about pouring capital into a no deal Britain.
Michael Brown, a senior currency analyst at Caxton FX, told Daily Star Online : “There’s no certainty with the pound right now as it is especially vulnerable to the on-going political uncertainties and developments related to Brexit.
“It fell to a more than two-year low against the US Dollar last week as markets began to once again price in the risk of a no-deal Brexit further to comments from Boris Johnson that the Irish backstop is ‘dead’, and reports that the suspension of Parliament to force through a no-deal Brexit was under consideration."
Since Britain voted to leave the EU the pound has fallen by 14% against the euro.
Last Wednesday it hit a six-month low of €1.105, dropping to $1.24 against the US dollar.
Analysts at Morgan Stanley say that were the UK to leave the EU without a deal on 31 October the rates could fall to £1 being worth $1.
That would threaten the all-time low of $1.04 reached briefly in early 1985.
