Sterling slumped to an eight-year low against the euro on Wednesday, which experts put down to Brexit uncertainty and stronger than expected growth in the eurozone economy.
The pound was down 0.5 per cent to 1.083 versus the euro as the London market closed, hitting its lowest level since October 2009.
But at the airports the exchange rate has sunk further with one pound buying customers less than a euro.
Research compiled by FairFX and Moneycorp showed the walk-up rate offered at London airports Gatwick and Stansted was just 0.949 euros and 0.921, respectively, to the pound.
At Heathrow, the Travelex desk was offering 1.037 euros to the pound on Wednesday, according to the research.
Southampton airport had the worst exchange rate where customers were offered just 0.872 euros to £1. For every £1,000, travellers would get just 872 euros.
Holidaymakers can purchase travel money online in advance and receive much closer to the official rate.
Customers ordering £1,000 worth of euros from Tesco online on Thursday morning would get €1,065, at an exchange rate of 1.0629.
Ian Strafford-Taylor, chief executive of travel money firm FairFX, told the Daily Mail: “Holidaymakers getting away from it all to make the most of the last bank holiday of the year need to be wary of buying currency last-minute at the airport.”
James Daley, director of consumer website Fairer Finance, told the newspaper: “Airport bureaux are becoming the pantomime villains of the summer.
“They have always offered bad rates but over the past couple of years the gap between the market rate and what we get seems to be getting wider and wider.”
The pound was also struggling against the US dollar, down 0.2 per cent at 1.278 on Wednesday.